Characterization and utilization of apple peel and grape stems extract constituents as green restraints for aluminum dissolution | Scientific Reports

Scientific Reports volume 14, Article number: 24170 (2024) Cite this article

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Different flavone extracts from apple peel and aldehydes from grape stems were investigated as restraints of the anodic aluminum dissolution procedure in 60% H3PO4:40% H2SO4. The potential-limiting current correlation for Al anode was assessed and associated with regularly improving apple peel and grape stems extract concentration (100 to 1000 ppm range). The limiting current reduces whereas retardation effectiveness (%) increases as the concentrations of apple peel and grape stems extract rise. Apple peel/grape stems mixture extract is pondered to have the most retardation impact. Apple peel and grape stems extract retardation mechanism depends on the adsorption manner at the aluminum metal, which was confirmed via scanning electron microscopy (SEM) and UV-VIS-NIR spectra which reflect that elevated extract concentration (1000 ppm) have a hopeful and positive impact on the Al surface quality. The activation energy and activation constraints (changes in enthalpy, entropy, and Gibbs free energy) were established, and suggestions for powerful interaction between the additives and the aluminum surface were conveyed. The extract items were inspected via Fourier transform infrared spectroscopy and Gc-mass. The apple peel and grape stems extract establish perspective as a natural electro-polishing green restraint. The weight loss data obtained is in excellent conformity with the result obtained by electrochemical measurements. The synergistic influence between apple peel/grape stems (S = 1.64–1.83 ) is noticeable. The lowest Ra and PV estimates are recorded via an apple peel /grape stems mixture, which achieves the greatest reflectance estimate and retardation effectiveness. This is recognized high active site number for apple peel /grape stems mixture extract.

The anodic remedy is a prominent surface enhancement procedure and metal and alloy coarsening. The anodic progression of the surface is furthermore described as electro-polishing. It is an electrochemical method for surface improvement via purposes of metal, or alloy deletion, that is broadly utilized in metals and alloy surface finishing and industries. In contrast through motorized polishing, electro-polishing supplies the main recompenses for creating a meticulously soft, submissive, and anti-corrosive metals and alloys surface, in the meantime the strain values restrained afterward handlings are very small1,2.

The electro-polishing surface phenomena are commonly categorized as interested in dual procedures: anodic flattening and anodic illuminating. Anodic flattening comes from the dissolution difference rate among tops and hollows on an estimated metal or alloy surface dependent on the current division or mass-transportation provisions. The electrochemical polishing benefits have extended notoriety, being revealed to be a perfect approach for refining a metal’s optimal coarseness while also significantly enhancing electrical conductance. Several acid management presently employed for metal surface electro-polishing give standard mirror completion via the exposed surface layer removal for the metal sheet. However, acid mixtures keep this clean electro-polished finish to the metal at the overhead of hydrogen corruption.

Alternatively, anodic illuminating is established to be attained under the tertiary current division states only. Meanwhile, anodic brightening entitles the absenteeism of crystallographic disbanding associated with the metal microstructure, alteration in the dissolution procedure from the surface-dynamic regulator of the diffusion controller situations is recommended for the progression of this microstructure-oblivious singularity. The electro-polishing mechanism is associated with the current circulation on the sample surface. The current allocation has been categorized as primary, secondary, tertiary, or quaternary dependent upon the aspects influencing it. The elementary current allocation is concerned by the ohmic opposition and its job in electro-polishing is contingent on geometric aspects such as anode-cathode distance and preliminary geometric surface shape to be polished. The secondary current allocation comprises the outcome of charge transport over potential along with the geometrical aspects. Concentration overpotential along with the above aspects comprises the tertiary current distribution and is fundamental circumstance to attain a smooth surface via electro-polishing. Hydrodynamic consequences also contribute to the current allocation. Hydrodynamics has been observed to be an important consideration for imperfections created through electro-polishing3,4.

Aluminum and its alloys have extraordinary financial and attractive materials for engineering purposes owing to its low cost, pale mass, and raised thermal and electrical conduction. The importance of materials arises from their significance in current society. The fused possessions of elevated reflectiveness and minimal absorption yield the aluminum used as a reflection in a diversity of optical machines, like lasers, stellar cells, interferometers, and astrophysicist devices. Aluminum and its compounds, however, are reactive substances and are susceptible to reaction. Because of its varied applications in industry and daily life, aluminum’s electro-chemical properties are the topic of a lot of research5.

Generally, many authors interested in aluminum polishing such as the electro-luminescence of aluminum during electropolishing in nitric acid were inspected via the impurity’s establishment in electro-polishing electrolyte6. The electro-polishing performance of high-transparency aluminum through supersonic disturbance was inspected7. Roughness and specular property investigation of commercial aluminum8. The dissolution performance of machine AA7150-T651 aluminum alloy9. The aluminum electro-polishing and its alloys in an ionic solution10. Aluminum alloys were electropolished with an ecologically approachable procedure11. Electro-deposition and electro-polishing of aluminum anhydrous aluminum chloride and trimethylamine hydrochloride12. Evaluation of aluminum electro-polishing in deep eutectic electrolyte13. Vitamin B’s impact on the morphology, roughness, and reflectance of electro-polished aluminum is investigated5.

The improvement of newfound chemicals is mainly interesting, as they should demand to conserve the excellent significance under various provisions, whilst being environmentally sufficient. There is encouraging anxiety concerning the harmfulness of electropolishing- additives in the industry. Regarding caring for the environment, poisoned substances broadly treated in industrialized procedures should be reinstated via green ecologically kindly ones.

Apple peel has unique flavonoids like quercetin glycosides. Different phenolic composites exhibited in apple peel are catechins, procyanidins, phloridzin, phloretin glycosides, caffeic acid, and chlorogenic acid14.

Grape stems contain useful phenolic compounds. Phenolic composites are identified for their antioxidant, anti-inflammatory, and anti-aging properties. Grape stems are remarkably full in these composites, involving resveratrol, flavonoids, anthocyanins, and tannins15.

In our investigation, a challenge is the reduction of the surface unevenness via easing the etched depths and flawlessness constructed on the surface, therefore, the surface levelness and brilliance might be enhanced.

Appropriately, the current research is targeted to accomplish galvanostatic polarization measurement to examine the EP procedure of pure aluminum in 60%H3PO4: 40% H2SO4 acid electrolyte in the attendance of apple peel and grape stem extract. The polishing extent is assessed through a detailed study relating the apple peel and grape stems extract influence of different concentrations.

This is attributed to their numerous advantages, including low toxicity, abundant availability, high cation exchange capacity, and favorable textural properties. It is great to hear about the ongoing efforts to find effective and environmentally friendly additives to dissolution baths. The current study aims to leverage the advantages of apple peel, and grape stems through the physical synthesis of apple peel–grape stems composite, the synergetic influence of apple peel-grape stems mixture, also the resultant surface morphology (investigated by SEM), surface roughness (AFM) and surface brightness (reflectance).

The electric cell applied in our research (Fig. 1) contains quadrilateral containers having 5 × 10 × 15 cm lengths using electrodes appropriate for the entire section. The electrodes are quadrilateral great purity aluminum pieces (99.99) of 10 cm height, 5 cm width, and 0.2 cm breadth. The anode-cathode distance is 14 cm. The electrical circuit consisted of a 20 V D.C. electric power; a varying endurance and a multi-extend ammeter are associated in a series with the cell. An elevated resistivity voltmeter is attached in equivalent through the cell to determine its voltage. The electro-polishing solution is composed of H3PO4 (85%) and H2SO4 (96%) mixture. Ten concentrations of ethanolic extracts with acid mixture are used ranging from 100 to 1000ppm. The continual anode potential is assessed as opposed to a reference work electrode consisting of an aluminum line submerged in a lugging pipe cup supplied with an acid mixture –plant extract solution like that in the cell. The lugging tube tip is 0.5–1 mm from the anode partition. From the polarization plots, the limiting current (polishing rate) is settled, which are outlined via raising the applied current step by step and determining the subsequent stable-state voltage. Before each trial, the anode back was shielded using polystyrene lacquer, and the active surface was cleaned via trichloroethylene, washed using alcohol, and finally cleansed in demineralized water that have resistivity > 18 mΩ. The temperature (± 0.5oC) is controlled by locating the cell in the thermostatic water container at variable temperatures (30-60oC).

The ordinary transportation electrical circuit.

Apple peel, and grape stems were bought from the regional shop, that the collection and use of any plant materials in this study is carried out in accordance with any National/International/Legislative/Institutional guidelines and regulations. A general statement such as “The plant collection and use was by all the relevant guidelines” is also accepted, rinsed with purified water then air dehydrated and individually cut down into face powder utilizing a blinder. Around 50 g of the crushed specimens were sodden in 1000 ml ethyl alcohol for 14 days (to improve the appropriate combination of ethanol along with crushed specimens ) at 25oC. The mixes were then riddled to eliminate any contamination and to attain sample excerpts. This standard plant extract was maintained in the freezer, and it is willing to be utilized to manage necessary concentration. The standard solution application was concluded via vaporizing a well-established of excesses volume to eradicate the solvent completely and assessing the remainder.

The scanning electron microscope pictures are regarded utilizing (JEOL, JSM-5300, scanning microscope, OXFORD device). So, the aluminum specimens are (1 cm ×1 cm).

The aluminum sections utilized for atomic force were divided into (3 × 3) cm dimensions. All specimens were washed via acetone, tap water then distilled water, EP procedure take place for samplings in the cell including various apple peel and grape stem extract concentrations. Afterwards, the specimens were cleansed via tap water then demineralized water, and kept these samples in desiccators till it was inspected. Three-dimensional AFM image for aluminum in 60% H3PO4:40% H2SO4 electrolyte -plant extract frees solution and 60% H3PO4:40% H2SO4 electrolyte -containing plant extract were obtained.

A Shimadz UV-3101 PC Spectrophotometer (UV-VIS-NIR) Scanning spectrophotometer is utilized to attain brightness degree of Al in the of 300–1500 nm range.

For FT-IR analyses, A Bruker Tensor 37 Fourier transform infrared spectrophotometer, device was utilized, dry apple peel and grape stems were utilized. The specimens were determined via blending along with potassium bromide. The fields were assessed in the 400–4000 cm−1scale.

GC assessment was conducted utilizing Gas Hewlett Packard HP5890 sequences II with split per split fewer injector and vessel line (28 m, 0.24 mm, 0.24 mm) combined with phenyl polysilphenylene Siloxane. The injection part and indicator heat were 270 and 305oC, correspondingly, and the oven heat were maintained at 85 C for 2 min, rising to 305oC at 22oC / min. Helium was utilized as transporter gas at a persistent stream of 1.0 ml per min. A capacity of 2 ml was inserted in the break less method and the elimination period were 2 min.

The MS (Hewlett-Packard 5889 BMS Engine) with certain ion observing (SIM) was utilized. It was conducted at 70 eV and examined pieces from 50 to 650 m/z.

The procedure conducted for individual components detection for plant isolate was established on chromatographic preservation indicators and by comparison the acquired MS along with those available in NIST archive.

Aluminium specimens used in mass loss procedures were cut mechanically into 3 × 3 pieces, abraded with 180, 320, 800, and 1200 grades of emery papers, washed using de-ionized water, degreased with ethanol, and dried. The specimens were weighed before and after immersion in an electropolishing bath. Trials were performed in triplicate to the reproducibility.

The plots demonstrate the normal I-V individuality for electro-polishing. Three areas relating to opposing, shining, and oxygen gas progression on the surface of anode are known to be dependent upon the employed potential. Primarily, the current linearly intensified from the origination of the voltage scan and turned up a plateau. This behavior is directed via the Ohmic endurance in the electrolyte. At elevated voltage, fluctuation is where both potential and current are located. After the straight range, the current persists continuously, though the voltage develops. They persisted to increase in potential results in an amplifying in current owing to oxygen progression16.

This province is of wonderful technical significance since electro-polishing may be accomplished via governing voltage in the variety of limiting current plateaus. Surface smooth out may be accomplished via managing the anode voltage at limiting current plateau where either a sheet is modelled on the anode surface or distribution of an acceptor to the anode develops rate restraining.

In the case of aluminum electropolishing systems which obey the acceptor procedure, the salt sheet was not constructed. As an alternative, there is a viscid film near to the anode surface. Aluminum and aluminum compounds have air established oxide layer of formless γ alumina that primarily stiffens on disclosure to the neutral aqueous solution with the crystalline hydrated alumina development17.

The anodic polarization plots for the aluminum anode that are electropolished in 60% H3PO4:40%H2SO4 electrolyte with the addition of plant extract of several concentrations (100–1000 ppm) are shown in Fig. 2a-c). A limiting current plateau can be observed in every anodic polarization plot. A noticeable reduction in the limiting current is noticed when the studied apple peel and grape stems extract are included (Tables 1 and 2). This proposes that the aluminum anodic polarization performance is appropriate and responsive to tiny concentrations of apple peel and grape stems. The monitored reduction in limiting current via the investigated apple peel and grape stems extract addition (Fig. 2a-c) is faithful to the acceptor system. When apple peel and grape branches were additional, it is credible that adsorption of such composites on and near the anode surface may lead to regulate ion diffusion procedure in three customs, specifically (i) satisfying up of surface echoing space and glooms (ii) the wobblier stuffing of the adsorbed layer at mountains assists the metal subtraction at an earlier rate than loss from valleys. Hence, surface flattening occurred owing to the crevice’s passivation being further stable, and it retard etching. Summits are a substitute for dissolving more quickly. (iii) By substituting water particles in this section. This procedure may alter the medium dielectric coefficient and reduce the number of water particles number that are accessible for cations solvating, hence lowering the cations distribution rate beyond the anode surface18.

Regular polarization plots for the EP of Al anode in 60% H3PO4: 40% H2SO4 at several concentration a, á) apple peel, b,b́) grape stems and c) apple peel-grape stems mixture.

If (IL)blank is the limiting current in the plant extract- free electrolyte and (IL)plant extract in the electrolyte-containing plant extract, then IE % may be evaluated from the subsequent equation:

The reduction in limiting current is dependent on plant extract concentration and nature.

The enhancement in plant extract concentration enhances the retardation effectiveness. This performance can be explained based on the effective interaction of the plant extract particle with the Al surface development. The adsorption scope rises via the enhancement in the concentration of plant extract resulting in intensified retardation effectiveness. The dissolution overcoming plant extract capability constituents initiates from the inclination to form each effective or ineffective chemical bond with Al atoms employing the oxygen electrons lone pair and π electrons in the benzene ring. These organic particles may adsorb on the metal/electrolyte boundary in one or more of the subsequent ways; (i) donor-acceptor connections among the aromatic ring p-electrons and vacant P-orbital of surface aluminum (ii) communication among nonbonding electron pairs of hetero atoms and vacant P-orbital of surface aluminum atoms5,18.

From the estimated values of retardation effectiveness percentage (IE %) (Tables 1, 2 and 3 and Fig. 4), the IE % of each investigated plant extract is concentration dependent.

The percentage retardation effectiveness improves as the plant extract concentration enhances at all concentration ranges investigated.

The extract retardation order is as results: mixture > apple peel > grape stems extract.

It may be demonstrated from Tables 1, 2 and 3; Fig. 2a-c that the anodic limiting current reduces while several apple peel and grape stems extract concentrations rise at all concentration ranges considered (100–1000 ppm) and IE% rises as the concentration of all these extracts rises; hence, the electropolishing procedure of aluminum is reduced subsequently. This may be ascribed to the subsequent evidence.

Adsorption of these particles on the aluminum anodic surface may create an adsorbed layer at the aluminum anodic surface; resulting in a reduction in the Al3+ ions diffusivity and a rise in the confrontation to the Al3+mass transference rate from anode surface to bulk solution; therefore, the aluminum electro-polishing rate may be reduced. Furthermore, additive adsorption on the aluminum surface depends essentially on their composition.

For apple peel extract retardation mechanism.

The apple peels show a remarkable retardation performance in electrolyte solution by decreasing the dissolution rate from 0.542 in blank solution up to 0.052 at 1000 ppm of apple extract (Table 1) that ascribed to which apple peels comprise a larger number of composites that comprise several hetero atoms like oxygen and unsaturated π electrons these atoms adsorb onto the metal surface and improve a shielding layer. The GC-MS investigation of apple peels described that Flavone 1 and Flavone 2 are the major constituents of the peels. These composites may adsorb on the metal surface through oxygen atoms in lone pair and form protecting layer, additional benefit of these compounds is that aromatic rings may also adsorb physically via Vander Waals forces that give rise to adherent and insoluble protecting layer then caused sturdy retardation behavior14,20. This result is consistent with current researches such as inhibition of corrosion of mild steel in simulated concrete pore solution prepared in sea water by an aqueous extract of apple juice21, also aqueous extract of punica granatum fruit peel as an eco-friendly corrosion inhibitor for aluminum alloy in acidic medium22.

For grape stems extract.

It’s established that the aluminum dissolution rate diminished substantially via strengthen the grape stems extract concentration from 0.542 in electrolyte mixture – grape extract free to its minimum value o.132 at 1000 ppm grape stem extract (Table 2). The retardation action of grape stems extracts since it comprises a variety of oxygen-containing compounds, and unsaturated composites. Those composites comprise unsaturated π electrons and hetero atoms that hold lone pairs (electronic density) which cooperate with the aluminum vacant p-orbitals and encourage a protecting film [Al- grape branches] composite on the surface that may separate the aluminum from the acid mixture electrolyte. The GC-MS investigation of grape stem extract represents that aldehydes are the main constituent. These compounds may adsorb on the aluminum surface via the oxygen atoms nonbonding pair and stimulate a protecting film to separate the Al from the aggressive species15,23. This result is consistent with current researches using a novel eco-friendly vapor phase corrosion inhibitor of mild steel24and grape pomace extract as a green vapor phase corrosion inhibitor25.

Effect for apple peel - grape stems extract mixture.

Using potential-dynamic trials to investigate the synergistic retardation between apple peel and grape stems, the proportion of the mixture was 1:1, was used. The potential-dynamic polarization plots of Al with apple peel-grape stems extract mixture are demonstrated in Fig. 2c; Table 3. As shown in Table 3; Fig. 2c, the combination of apple peel and grape stems show a stronger dissolution retardation effect, where the limiting current decreases significantly.

Retardation behavior of the mixture is owing to the extract particles at the electrode- electrolyte interface may raise the interfacial viscosity by resulting reduction in the electroactive ions diffusivity. This cause delays the solution flow past the electrode surface and subsequently reduction in the limiting current values.

Moreover, the extraordinary mixture retardation behavior aims compelling bonding of the efficient complexes and aluminum surface due to heteroatoms (O) nonbonding electrons and p- orbital preventing the energetic sites and reducing the dissolution rate. Consequently, bonding among additive particles and aluminum surface happens via participation of the oxygen atoms electrons (OH and CO groups) located in the recognized composites of the ethanolic extract of apple peel and grape stems with vacant Al P-orbital. Mixture particles may absorb on the Al surface based on donor–acceptor collaboration among aromatic rings p-electrons and vacant P-orbital of Al26.

To estimate the nature (additive, synergistic, or antagonistic) of the two-extract synergistic contact was when collective influence was > additive influences, however antagonistic interactions were when combined influences were < additive. Synergistic effects are the influence when chemical substances or biological structures interact leading to an overall influence that is higher than the sum of individual effects of any of them. Synergistic influences are the merger of an influence of at least two substances making an affect that is more substantial than both might have demonstrated by themselves27.

The synergist parameter could be calculated from the following formula:

where IA is the inhibition efficiency in the presence apple peel extract (APE), IB is the inhibition efficiency in presence of grape stems extract (GSE), IAB is the inhibition efficiency in presence of the combination of apple peel and grape stems. S > 1 signifies that the mixture system has a noticeable synergistic effect. S ⩽ 1 indicates that the synergy is not substantial or there is an antagonistic effect. The greater the S value, the more powerful the synergy among the additives. The estimated synergist parameter of APE / GSE is S APE/GBE = 1.64–183), the synergy between APE and GSE is obvious. Also, it is indicated that stabilization of the adsorbed layer of apple peel /grape stem composite on aluminum surface .

The organic composites are observed in apple peel, and grape stems were discovered via GC–MS analysis. The molecular formula, molecular weight, retention time (RT) and % compositions are described in Table 4.

The hetero-atoms subsistence, benzene ring, alongside various functional groupings (hydroxyl, carbonyl and carbon-carbon double bond) in plant extract might support their particles to adsorb on Al -solution interface to diminish the Al dissolution. In this research, the FTIR (Fig. 3) was commissioned to distinguish whether the plant extract includes certain of these efficient groups or not.

FTIR spectra of ethanolic plant extract before and after EP. (a) apple peel, (b) grape stems.

Apparently:

For apple peel: obvious band detected at 3665 − 3280 and 3680 –3600 cm−1 indicate the opportunity hydroxyl association incidence, nevertheless abroad band at 3600 cm−1 suggest the possibility of water hydration. The bands are on account of loose or weakly hydrogen connected water particle to the oxygen surface of tetrahedral covering water particles, water-water hydrogen bond. The band at 1267 and cm−1 is related to C-O that became 1240 cm−1 after EP. The absorption band at 1037 & 1025 cm−1may be recognized as C-O-C that changed into 1060 &1200 after EP. The C-H at 965, 780 and 823, 782 display the benzene ring presence that shifted to 830,765 and 860,770 after EP28.

For grape stems: An expansive broad peak at 3373 cm−1 of O-H band proves the existence of alcohols combinations and carboxylic acids that shifted to 3380 after EP. The precisely mid-intense peak at 1737 cm−1 ascribed to carbonyl group C = O that lead to aldehydes, ketones and carboxylic acids presence that shifted to 1750 cm−1 after EP. The moderate sharp peak at 1628 cm−1 signifies the unsaturated compounds (alkenes) presence that shift to 1642 cm−1 after EP. The alkanes presence is confirmed via a stretching band at 2943 cm−1 that changed to 2956 cm−1 after EP. The absorption peak at 1226 cm−1 proves the esters and ethers presence that changed to 1234 cm−1after EP29.

The observed alteration in the bands prior to and afterwards EP to suggest the development of [Al -plant extract] composite. Additionally, it is noticed that nearly whole the summits examined for dried up plant extract beforehand EP are additionally observed for plant extract afterward EP (Fig. 4).

Percentage retardation effectiveness (% IE)- concentration dependence plots for aluminum in acid mixture electrolyte containing several concentrations of (a) apple peel ), (b) Grape stems, and (c) apple peel-grape stems mixture.

Figure 5 shows the UV-Visible spectrum of apple peel and grape stems extract. As seen in Fig. 5a, the solution having Al3+ ions displays three absorption bands at 209, 252 and 816 nm. In Otherwise, apple peel extract solution reveals two bands only at 229 and 279 nm. Al3+ ions adding to apple peel extract results in substitute the 252 and 816 nm absorption bands of Al3+ ions by powerful absorption bands at 323 and 813 nm investigative of Al-apple peel extract complex formation. But, grape stems extract containing solution demonstrates only two bands at 218 and 268 nm. Al3+ ions addition to grape stems extract lead to a change in the 209, 252, and 816 nm Al3+ions absorption bands by powerful absorption bands at 257 and 807 nm which indicate that Al- grape stems extract complex formation. Therefore, Al-plant extract may be as a stable complex adsorbed over the metal surface resulting in retardation influence3,4.

UV-visible spectrum of (a) apple peel and (b) grape stems.

The weight of the aluminum specimen was measured before and after EP. The electropolishing rate was calculated according to Eq. (3)

where Weight before EP is the aluminum specimen weight before electro-polishing, Weight after EP is the weight after electro-polishing and post-cleaning. The area is the aluminum specimen area (3 cm x 3 cm) and Time is the electro-polishing time in s (seconds). The aluminum specimens were electro-polished at a 25 °C bath temperature. (Table 5) show electro-polishing rate measurements confirmed the data obtained from potentiodynamic measurements, where the addition of ethanolic plant extracts retards the dissolution rate and it is observed that retardation behavior amplified via rising immersion time The retardation in dissolution rate in the presence of ethanolic plant extracts via immersion times increase may be as a result of adsorption of more ethanolic plant extracts particles on the Al surface, as immersion time increases leading to more effective protection of the sample Al from dissolution, This phenomenon means that the ethanolic plant extracts particles were adsorbed on the surface of the metal surface and a shield or physical barrier are formed3, hence, there was a decrease in dissolution rate.

The temperature is attained to be a very essential constraint for electro-polishing. Limiting current plateau encourages via temperature increasing from 30 to 60oC (Table 6).

The plateau current enlarges through temperature rising. This data might be associated to Eq. 5 for the limiting current value.

where A is Temperature independent pre-exponential, Ea = Activation energy (kJmol−1),T is temperature in (kelvin, K ) and R the gas constant (8.314 J K−1 mol−1).

Figure 6 displays a curve of ln IL vs. T-1in acid mixture electrolyte in the non-existence and existence of 1000 ppm apple peel and grape stems extract. The linear fit slope of the data points as indicated in Fig. 6, might admit supposing the reaction activation energy. In the present case, the activation energy (Ea is approximately 13.11 kJ mol−1. Contemplating the predictable activation energy for the electro-dissolution procedures for Al metal while in the presence of apple peel and grape stems extract is 65.31 and 36.64 kJ mol−1 respectively. The greater Ea values are a respectable indication of the great retardation performance of plant extract for the Al electro-dissolution procedures, also may be associated via growing of the double layer thickness that improves the Ea of the dissolution progression30.

(a) Arrhenius and (b) Transition state plot of the Al dissolution reaction in acid mixture electrolyte containing 1000 ppm of apple peel and grape stems.

The reaction activation considerations (∆H# ,∆S#and ∆G#) were estimated from the following Eq.

Where h is the Plank,s constant, N is Avogadro’s number, ∆H# is the enthalpy of activation, ∆S# is the entropy of activation and ∆G# is free energy of activation. The activation parameters data represented in Table 6 which indicates that:

The ∆H#, positive signs indicate the endothermic characteristics of aluminum electro-polishing5,30.

The negative ∆S#values mean that the activated composite in the rate-controlling step signifies a correlation rather than a division step, implying that a reduction in disturbing occurred on proceeding from reactants to the activated composite31.

The ∆G#values in the presence of apple peel and grape stems extract were more positive than that for acid electrolyte -plant extract free solution revealing that in plant extract presence, the activated complex develops less stable as related to its absence32.

Surface characterization includes three techniques.

Scanning electron microscope, SEM.

Reflectance.

Atomic force microscope.

As displayed in Fig. 7a-g, the surface geomorphology after EP in the presence of several concentrations of apple peel and grape stems.

For 500 ppm apple peel (Fig. 7c), there is enhanced surface morphology where the Al surface appears smooth and identical to some degree, but there a very small spots that form, and very minor protrusions are illustrated obviously. When the apple peel concentration raises to 1000 (Fig. 7d) ensued in the creation of an evener, leveled, and smooth surface, signifying improved surface growth in the APE concentration caused by the reaction area reduction, a phenomenon identified as the obscuring influence of dissolution retardation substances on the metal surface.

For 500 grape stems are revealed in (Fig. 7e), where levelling and brightening are appearing. There is an excessive significant improvement in surface brilliance is noticed related to blank, but some granule margins are characterized on the surface of Al, but it seems regular and even, on the other hand, the addition of 1000 ppm grape branches (Fig. 7f). The surface look is silky and completely featureless, grain boundaries are wholly disappeared. This performance may be owing to the participation of grape branches in the surface cavities, so appear wholly even and regular33.

Figure 7g shows the Al surface morphology after addition of 1000 ppm apple peel -grape stems extract to electropolishing bath, the aluminum sampling has an improved morphology uniform, and an uneven surface appearance is obtained.

The several outlines formation throughout electro-polishing may be described via field-supported metals dissolution. Through electro-polishing, a double layer is established on the solution electrolyte interface close to the continuous-potential metal surface as ions are concerned to it below the electropolishing voltage action. This sets up a voltage descent regular to the aluminum –electrolyte boundary. The electrolyte confines natural particles such as plant extract components. The potential gradient decreases the desorption of the natural particle and subsequently, crowns, with greater voltage descents, are differently obscured via these particles. The Al dissolution is then delayed at the crowns and troughs dissolve quicker. This disrupting procedure is responded via a curving steadying procedure which improves surface Al on a dipped surface over dissolved Al3+ particles. Therefore, brief wavelength instability is dampened. More prominently, as trenches dissolve greater, the stabilizing influence of the valley improves whereas the disrupting potential descent in the double coat declines. Accordingly, the predictable equilibrium profusion of the outlines is achieved where the two-curvature determined systems equilibrium to produce normal outlines.

In other words, through the anodic dissolution, the anode dissolution proportion is lingering and is the restricting impact. Consequently, the electro-chemical reaction is controlled via diffusing procedure. Owing to the diffusive procedure, a viscid film will be created on the anode. Respecting the electrolyte bulk, this film has a greater thickness and superior electric resistivity. The shielding layer depth is larger in gaps than predictions. The current density of protrusions is superior to in gaps. Therefore, protrusions dissolve more quickly than gaps, and this creates a surface-leveling influence34.

From the result of the surface morphology study, it can be concluded that. Obviously, the electropolishing behavior of the Al surface at 35oC is substantially affected by the concentration of several types of plant extract.

(a) Raw sample before polishing. (b) After electropolished (blank) at 35oC. (c) After EP + 500ppm apple peel. (d) After EP + 1000ppm apple peel. (e) After EP + 500 ppm grape stems. (f) After 1000 ppm grape stems. (g) After EP + 1000 ppm mixture.

The Vis-IR spectra of unprocessed sample, Al that electropolished acid mixture (blank) and Al that electropolished acid mixture electrolyte comprising 1000 ppm of apple peel, grape stems and apple peel-grape stems mixture is established in Fig. 8.

It is observed that the reflectance of electro-polished samples is greatly influenced through the plant extract type. The sampling reflectance that electro-polished at acid mixture improves associated with unprocessed sample, where the specular reflectivity estimates before EP is 20.94. After an EP in acid mixture is 39.0. Great reflection possessions are obtained. By addition of 1000 ppm grape stems, 1000 ppm apple peel, and 1000 ppm apple peel-grape stems, the surface brightness degree and reflectance are enhanced to 62.12, 78.22 and 83.31 respectively.

The shielding film development on the anode is extremely important. The anode film is a thin layer of solid substance or adsorbed particles. The polishing completion is to be respected owing to a diffusion-regulated anodic dissolution technique being set up during the anode film and layer. The insulating layer intensity and opposition improves via plant extract constituents’ addition. It is convincing that the adsorption of the investigated plant extract constituents complements, the performance of the natural anodic layer in developing the surface micro-structure, i.e., plant extract constituents may enhance the shielding layer breadth35.

The reflectance plot displayed in Fig. 8 is in excellent agreement with micro-structural and roughness statics, indicating an excellent reflectance percentage. Grain borders and grain adjustments create light diffraction, reducing the reflectance.

The Vis-IR spectra of electropolished specimens.

The surface roughness of the electro-polished aluminum sample and, several roughness estimates have been expressed in Fig. 9a-f, which is three-dimensional AFM image for aluminum in 60% H3PO4:40% H2SO4 electrolyte -plant extract frees solution and 60% H3PO4:40% H2SO4 electrolyte -containing plant extract. The data obtained from AFM measurements including average roughness Ra(µm), root mean square roughness Rq(µm), maximum peak-to-valley height Rz(µm) and peak-to-valley ratio, the surface roughness will be decreased via plant extract addition. Since the Ra and Ra trends are almost the same, just Ra values are supplied for the subsequent treatment. It is viewed that the raw Al specimen records the greatest surface roughness (0.77 μm), while, the electro-polished Al with a low Ra value of 0.52 μm is gained from the electrolyte including 60% H3PO4:40% H2SO4 electrolyte -plant extract frees solution. EP in the electrolyte comprising phosphoric acid, sulfuric acid, and apple peel and grape stems extract might be not the same as from the case holding phosphoric acid and sulfuric acid only. Therefore, their comparable surface roughness constraints are primarily reduced. Ra value are, 0.24, 0.16 and 0.04 μm in the presence of1000 ppm grape stems, 1000 ppm apple peel and apple peel -grape stems mixture.

In addition, water particles are counted as bulk acceptor particles, supporting essential ions to react with Al3+produced from the Al anodes dissolution in the suggested procedure. This result indicates that the solution particles may absorb on the sarcastic peaks and reduce the peak dissolution rate, resulting in homogeneous consistent dissolution rates among peaks and valleys and identical surface leveling. The minimum Ra and PV values are accomplished by an apple peel-grape stems mixture, that reports the maximum reflectance value and retardation effectiveness. This is ascribed to the combination effect of both constituents extract, which may attain excessive compacted surface coverage that results in vast contribution of both constituents extract like flavones and aldehydes particles in the Al surface cavities, so they seem smoother, and uniform than others36.

(a) Three-dimensional AFM image for aluminum after electropolishing in 60% H3PO4:40%H2SO4 electrolyte without addition(blank). (b) Three-dimensional AFM image for aluminum after electropolishing in 60% H3PO4:40%H2SO4 electrolyte + 500 ppm apple peel extract. (c) Three-dimensional AFM image for aluminum after electropolishing in 60% H3PO4:40%H2SO4 electrolyte + 1000 ppm apple peel extract. (d) Three-dimensional AFM image for aluminum after electropolishing in 60% H3PO4:40%H2SO4 electrolyte + 500 ppm grape stems extract. (e) Three-dimensional AFM image for aluminum after electropolishing in 60% H3PO4:40%H2SO4 electrolyte + 1000 ppm grape stems extract. (f) Three-dimensional AFM image for aluminum after electropolishing in 60% H3PO4:40%H2SO4 electrolyte + 1000 ppm apple peel -grape stems mixture.

The addition of apple peel and grape stems extract to the electro-polishing electrolyte leads to a reduction in limiting current.

Apple peel and grape stems extract controls dissolution rate of Al L via improving surface viscosity, that induce electrolyte planarization capacity.

Ea increased in electrolyte containing the apple peel and grape stems extract which are great approval of the effective retardation performance of apple peel and grape stems extract for the electro-dissolution procedures for Al metal.

The electropolishing performance of Al surface is substantially influenced via temperature and concentration of apple peel and grape stems extract.

Corresponding to SEM, UV-VIS-NIR Spectra and surface roughness data, addition of 1000 ppm of apple peel and grape stems extract to the electrolytic solution was particularly efficient to improve surface characteristic .

By addition of ppm grape stems, 1000 ppm apple peel, and 1000 ppm apple peel-grape stems, the surface brightness and reflectance degree are enhanced to 62.12, 78.22 and 83.31 respectively.

Ra value are, 0.24, 0.16 and 0.04 μm in the presence of 1000 ppm grape stems, 1000 ppm apple peel and apple peel/grape stems mixture.

The calculated synergistic parameter of apple peel/grape stems is 1.64–1.83, the synergetic effect among them is noticeable.

The adsorption layer of apple peel/grape stems mixture on the Al surface may fill each other to establish a thicker layer, and the synergistic dissolution retardation influence among the apple peel/grape stems is recognizable.

The least Ra and PV values are attained via apple peel /grape stems mixture, that records the elevated reflectance value and retardation effectiveness. This is accredited to great active sites amount for apple peel /grape stems mixture extract, that may accomplish excessive compact surface coverage.

The datasets used and/or analysed during the current study available from the corresponding author on reasonable request.

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Chemistry Department, Faculty of Science, Alexandria University, Alexandria, Egypt

F. M. A. Abouzeid

Department of Basic Engineering Science, College of Engineering, Imam Abdulrahman bin Faisal university, Dammam, Saudi Arabia

Sultanah Alshammery

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sultanah al shammary1- prepared Fig. 2- experimental work3- review the manuscriptfatma abouzeid1-the idea2-experimental work3-data analysis 4-writing discussion and interpretation.

Correspondence to F. M. A. Abouzeid.

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Abouzeid, F.M.A., Alshammery, S. Characterization and utilization of apple peel and grape stems extract constituents as green restraints for aluminum dissolution. Sci Rep 14, 24170 (2024). https://doi.org/10.1038/s41598-024-73592-5

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Received: 18 January 2024

Accepted: 19 September 2024

Published: 15 October 2024

DOI: https://doi.org/10.1038/s41598-024-73592-5

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