Design of Phytic Acid Crosslinked Xerogels as Organic Photocatalysts for Visible Light‐Assisted Degradation of Dyes

Extensive research is being carried out on the degradation of water pollutants using various strategies to overcome the global water crisis. In the present study, xerogels as a better alternative is utilized to metal oxides for the photocatalytic degradation of toxic water pollutants such as dyes. Xerogels of polyaniline (PANI) and polypyrrole (PPy) are synthesized using phytic acid as a dopant as well as cross‐linker in the weight ratios of 1:1, 1:2, and 2:1 via simple chemical oxidative polymerization. The synthesized xerogels are analyzed for their spectral, morphological, thermal, and optical properties using FTIR, UV–vis, XRD, SEM, and TGA techniques. The xerogels are also tested for their photocatalytic activity against textile dyes – Methylene Blue (MB), Alizarin Red S, (ARS), Rhodamine B (RhB), and Methyl Orange (MO). Among all the composite xerogels, PANI/PPy‐2/1 showed excellent degradation efficiency of 91% for MB dye, 88% for RhB dye, 96% for ARS dye, and 92% for MO dye respectively. The composite PANI/PPy xerogels showed better degradation efficiency than their pristine counterparts. The fragments of the degraded dyes are examined using the LCMS technique and a tentative dye degradation mechanism is proposed.


Introduction
Textile industries utilize various kinds of dyes during the printing process which are released into the water bodies. [1]The DOI: 10.1002/admi.202400046textile industry mainly uses reactive sulphur, acid/basic direct dyes, and dispersed dyes.Based on their solubility in water, disperse and sulphur dyes are easily separated from the effluent, while basic and acid dyes are difficult to remove using standard methods for separation. [2]Methylene blue (MB) dye is extensively used in a variety of industries and is known to cause health issues such as nausea, vomiting, severe perspiration, irregular breathing, and mental abnormalities. [3,4][7][8][9] For the aquatic systems, it may even prevent light from passing through water thereby harming the aquatic life.15] etc. Porous organic materials (POMs) and microporous organic polymers (MOPs) have shown to be effective as adsorbents for cleaning dye-contaminated water bodies. [16]However, the research on MOPs/POMs in wastewater treatment for dye removal is still in its early stages. [17,18][21] It also provides the benefit of minimal sludge production. [11,12]The ability to use sunlight to create hydroxyl radicals is another benefit of degradation via heterogeneous photocatalysts. [13,14][27] Moreover, the issue of toxicity using the metal oxides is always a concern as it is difficult to remove these photocatalysts after water treatment.In this regard, conjugated polymers offer a significant advantage over traditional molecular photocatalysts in terms of structural design, stability, and reusability. [23]ecently, researchers have focused on the use of polymers for carrying out metal-free photocatalytic degradation of water pollutants.The modification of polymers as photocatalytic materials to give them "hydrogel-like" qualities and increasing the number of active sites on the surface, is desirable to obtain efficient photocatalytic activity.Lately, polyaniline (PANI) based hydrogels have been reported to be used as photocatalytic materials due to their unique electrical conductivity, a highly interconnected open framework, and the ability to function without a template.Although PANI and polypyrrole (PPy) hydrogels have been reported earlier, no work has been reported on the photocatalytic activity of composite hydrogels of PANI and PPy.In the present work, we have, for the first time, synthesized composite xerogels of PANI and PPy in different weight ratios using phytic acid as a cross-linker and dopant.The synthesized xerogels revealed excellent photocatalytic activity for the degradation of both anionic and cationic dyes.The xerogels also revealed pH-dependent photodegradation which could be potentially utilized for selective dye degradation in polluted water bodies.

IR Analysis
The IR spectra of the xerogels are provided in supporting information shown in Figure S1 (Supporting Information).The PANI xerogel revealed a characteristic NH peak ≈ 3100 cm−1.The peak of C═C benzenoid ring stretching was observed at 1566 cm−1, while that of the quinoid ring was found at 1443 cm−1.The peaks at 1048 and 1112 cm−1 were associated with the C─N stretching modes and the C─N stretching of the secondary aromatic ring was noticed at 1242 and 1299 cm−1 respectively.The peak at 1128 cm−1 was associated the aromatic C─H in-plane bending vibrations, while the peaks at 608, 722, and 806 cm−1 were correlated to the presence of an aniline aromatic ring.[36] The peak at 1000 cm −1 was present in all of the samples confirming the presence of phytic acid.The xerogels revealed peaks correlated to PANI and PPy thereby confirming their polymerization and formation of composite xerogels.

SEM Analysis
The SEM images of PANI and PPy, Figure 1a,b were significantly different from composite xerogels.The PPy xerogel, Figure 1b, showed globular morphology, while the PANI xerogel, Figure 1a, revealed a rough and porous 3-D morphology.
The diffused porous structure of xerogels was due to the higher degree of crosslinking by phytic acid.[ 37 ] The morphology of the composite xerogels with varying concentrations of PANI and PPy showed the predominant morphology of PANI or PPy depending on their concentration in the xerogel.The xerogel, PANI/PPy-1/1, Figure 1c, showed a homogeneous morphology, while the one with higher loading of PANI, that is, PANI/PPy-2/1, Figure 1d showed the formation of large globules similar to the ones observed in pure PANI.The xerogel PANI/PPy-1/2, Figure 1e, showed a predominant morphology similar to that of pristine PPy xerogel.All xerogels showed a mesh-like interconnected network formation in all cases.

DLS Studies
The DLS profiles showed the size distribution in the xerogels (Figure S2a-e, Supporting Information).The particle size was found to be higher in PANI than in PPy.The particle size was found to vary with the loading of PPy and PANI in xerogels.The PANI/PPy-1/2 and PANI/PPy-2/1 xerogels showed higher particle size as compared to PANI/PPy-1/1.

XRD Studies
The XRD patterns of synthesized xerogels revealed broad peaks (Figure S3, Supporting Information).The PANI/PPy xerogels revealed diffuse and low-intensity peaks centred between 2 = 15°a nd 25°.The composite xerogels also revealed a semi-crystalline morphology similar to the pristine xerogels.The broad peaks in xerogels confirmed the presence of a short range ordered structure. [38]

TGA Studies
The TGA of PANI xerogel, Figure 2, revealed 10 wt% loss at 100 °C, while 20 wt% loss was found at 300 °C.At 600 °C, the weight loss was ≈ 44%.In the case of PPy xerogel, 15 wt% loss occurred at 100 °C, while at 400 °C, the weight loss was found to be 48%.The complete degradation in the case of PPy xerogel was noticed at 600 °C.In the case of PANI/PPy-1/1 composite xerogel, the weight loss was 12% at 100 °C and 25% at 300 °C.
The composite xerogels were found to be thermally stable as compared to pristine xerogels suggesting that the loading of either PPy/PANI in higher amounts increased the thermal stability due to the increase in crosslinking and formation of mesh-like network as observed in the SEM studies.

UV Analysis and Bandgap
The pristine PANI xerogel, Figure 3a, revealed intense peaks at 264 and 296 nm attributed to  - * transition, and the peak at 362 nm was associated with n- * transition.The PPy xerogel, Figure 3b, showed an intense sharp peak at 262 nm due to  - * transition, while the peak at 357 nm was associated with n- * transition.The UV peaks of PANI/PPy-1/1 composite xerogel, Figure 3c, showed sharp peaks at 262 and 292 nm.The UV spectrum of PANI/PPy-1/2 composite xerogel, Figure 3d, exhibited peaks at 262, 292, and 360 nm.The PANI/PPy-2/1 composite xerogel, Figure 3e, displayed peaks at 261 and 288 nm.The peaks at lower wavelengths corresponded to  - * transitions.The n- * transitions were found to be absent in composite xerogels presumably due to a higher great extent of crosslinking by phytic acid.The UV spectrum of xerogels revealed hypochromic shift in all of the synthesized xerogels as compared to pristine PANI and PPy xerogels.The hypochromic shift of the peaks was attributed to the torsional strain in conducting polymeric chains due to extensive cross-linking by phytic acid.The optical bandgap of the xerogels was calculated using a tauc plot.
The bandgap for PANI/PPy-1/2 was found to be 1.79 eV, while that of PANI/PPy-1/1 xerogel was computed to be 2.13 eV.The bandgap for PANI/PPy-2/1 was calculated to be 2.24 eV.The bandgap for PANI and PPy xerogels was calculated to be 2.59 and 2.69 eV, respectively.The bandgap was found to follow the order: PPy > PANI > PANI/PPy-1/2> PANI/PPy-1/1> PANI/PPy-2/1.It can therefore be concluded that the composite xerogels showed a decrease in bandgap which reflected their higher photocatalytic ability under visible region.

Photodegradation Studies
The xerogels were examined for their photocatalytic activity.The blank experiments are given in supporting information as Figure S4 (Supporting Information) and did not show any significant change in the UV spectra in the absence of light as well as in the absence of catalyst.To study the effect of catalyst concentration on photocatalytic degradation of dyes, the concentration of photocatalyst was varied from 50, 75 mg up to 100 mg for 80 ppm of dye concentration.It was observed that upon increasing the concentration of photocatalyst, the dye degradation increased.Maximum degradation was observed for 100 mg catalyst concentration used against ARS dye.The highest degradation of 96% was observed using 100 mg of PANI/PPy-2/1 composite xerogel as photocatalyst, Figure 4e, and the lowest of 52% was observed using 50 mg of PPy xerogel as photocatalyst, Figure 4b.However, 100 mg of PANI xerogel showed 70% degradation for ARS dye, Figure 4a.The PANI/PPy-1/2 composite xerogel (100 mg), Figure 4c, showed 85% degradation against ARS dye, while 90% degradation was achieved using PANI/PPy-1/1 composite xerogel as photocatalyst, Figure 4d.For the MB dye degradation, the PANI xerogel showed ≈ 70% degradation, Figure 5a, while the PPy xerogel revealed 65% degradation using 100 mg of the photocatalyst, Figure 5b.The PANI/PPy-1/2, and PANI/PPy-1/1, composite xerogels, Figure 5c,d, showed almost 80% degradation, while PANI/PPy-2/1 composite xerogel revealed 86% degradation, Figure 5e.Maximum degradation was observed when 100 mg of PANI/PPy-2/1 composite xerogel was used as photocatalyst, Figure 5e, which exhibited 91% dye degradation.The % degradation using 50, 75, and 100 mg of PANI/PPy-1/1 was calculated to be 52%, 71%, and 79% respectively.The PANI xerogel revealed 41%, 58%, and 64% for 50, 75, and 100 mg catalyst concentrations respectively.PPy-xerogel (100 mg) showed 60% dye degradation.
To further study the photocatalytic performance of PANI/PPy-2/1 composite xerogel, the degradation against RhB and MO dyes was also investigated (given in supporting information as Figure S5a-d, Supporting Information).Similar procedure was followed as mentioned in case of MB and ARS dye.The effect of concentration as well as the effect of catalyst on the degradation efficiency was studied.The findings correlated well with that of MB and ARS dye.As the concentration of the dye increased, the rate of degradation decreased.The % degradation in case of MO dye for 50, 30, and 10 ppm dye solutions was found to be 37%, 54%, and 73% respectively.In case of RhB dye, the degradation was calculated to be 70%, 62%, and 52% for 10, 30, and 50 ppm dye solutions, respectively.For studying the effect of catalyst concentration on the rate of degradation, the concentration of the catalyst was varied and degradation was found to increase as the concentration of catalyst increased similar to the degradation trend observed for MB and ARS dye solutions.The % degradation for RhB dye using 50, 75, and 100 mg catalyst concentration was calculated to be 52%, 70%, and 88%, while for MO dye, it was found to be 73%, 83%, and 92% respectively.

Zeta Potential and Effect of pH
The important factors that influence the rate of photodegradation are pH and zeta potential.The pH of the medium is responsible for the development of surface charge on the catalyst and hence effects the rate of photodegradation.The effect of pH on the degradation efficiency of PANI/PPy-2/1 composite xerogel was carried using pH values ranging between 2-12, Figure 8a-c.The surface of composite xerogel revealed a positive potential at lower pH.With the increase in the pH of solution, the negative potential on the PANI/PPy-2/1 xerogel also increases, Figure 8a.Since, MB and ARS dyes are cationic and anionic dyes respectively, there occurs an electrostatic interaction (repulsive and attractive) between the charged dyes and the catalyst.The photodegradation for MB dye was 78% and 93% at pH 2 and pH 9 respectively.For ARS dye, the degradation was 98% at pH 2 and 64% at pH 12. MB dye is neutral at low pH and with an increase in pH, the MB dye becomes positively charged.The xerogel develops negative charge resulting in an intense electrostatic interaction between the dye and the catalyst. [36]Thus, for MB dye, the degradation efficiency was found to increase with the increase in pH up to the value of 9. [38,39] Beyond pH 9, there was a decrease in the photodegradation efficiency which was correlated to the increased attraction between the methylene blue and OH - ions present in the dye solution which lowered the degradation efficiency as mentioned by other authors. [2]For ARS dye, higher degradation occurred at lower pH values due to the electrostatic interaction between the xerogel and the negatively charged dye thereby leading to maximum degradation of the dye.[41][42] MO dye showed higher degradation efficiency at lower pH, while RhB dye showed higher degradation efficiency at high pH values.

Radical Scavenging Experiment
To further understand the process of photocatalysis in the presence of composite xerogels, radical generation studies were conducted to determine the reactive oxidative species responsible for •-scavenger) (5 ml, 5 Mm), t-butyl alcohol (t-BuOH) ( • OH scavenger) (5 ml, 5 Mm) and ethylene diamine tetra acetic acid (EDTA) (h + scavenger) (5 ml 5 Mm), were added into dye solution and exposed to visible light irradiation for 120 and 90 min in presence of the xerogels.For PANI xerogel, the ARS dye degradation was found to decrease in the presence of EDTA to 59%, while for PBQ, it was found to be 50%, Figure 9a.The degradation efficiency was further reduced to 38% in presence of t-BuOH.Similarly, in case of PPy xerogel, Figure 9b, the degradation efficiency in presence of EDTA was 56%, while for PBQ and t-BuOH, it was 38% and 24%, respectively.The degradation efficiency for composite xerogels also displayed a decrease in the degradation efficiency in presence of scavengers.For PANI/PPy-1/1, Figure 9d, the degradation efficiency was found to be 78%, 64%, and 48%, respectively in presence of EDTA, PBQ, and t-BuOH.For PANI/PPy-2/1 xerogel, the degradation efficiency showed 80% reduction using EDTA, Figure 9e.In presence of PBQ and t-BuOH, it was calculated to be 68% and 53% respectively.The PANI/PPy-1/2 composite xerogel, showed the degradation efficiency to be 64% in presence of PBQ, Figure 9d.In presence of EDTA and t-BuOH, it displayed a degradation efficiency of 72% and 43% respectively.The PANI xerogel, showed 58% degradation in presence of EDTA as a scavenger in MB dye solution, Figure 9a.In presence of PBQ and t-BuOH, the degradation efficiency was found to be 47% and 27% respectively.The degradation efficiency was recorded as 54%, 43%, and 23% respectively for PPy xerogel, using EDTA, PBQ, and t-BuOH, Figure 9b.For PANI/PPy-2/1 composite xerogel, Figure 9e, the degradation efficiency was recorded as 79% in presence of EDTA, 67% in presence of PBQ, and 52% in presence of t-BuOH.The degradation efficiency in case of PANI/PPy-1/1 composite xerogel in presence of EDTA was found to be 73%, Figure 9c.In presence of PBQ and t-BuOH, it was found to reduce to 65% and 48%.Also, for PANI/PPy-1/2 xerogel, Figure 8d, the degradation efficiency was found to be 38% in presence of t-BuOH.In presence of PBQ and EDTA, it was found to be 55% and 63% respectively.

Recyclability Test
The recyclability tests, demonstrated that the synthesized xerogels (100 mg) showed 81% degradation for MB dye and 87% degradation of 80 ppm ARS dye solution demonstrating significant catalytic activity even after six cycles, confirming their exceptional stability and reusability (Figures S6 and S7, Supporting Information).Due to their relatively high reusability characteristics, the composite xerogels could be utilized as potential photocatalyst for wastewater remediation.

LCMS Studies and Degradation Pathway
The degraded fragments obtained using PANI/PPy-2/1 as photocatalyst were confirmed using LCMS data (Figure S8a-d, Supporting Information), and a tentative degradation pathway was proposed as shown in Scheme 1.The fragmentation of the dye was carried out by the • OH species generated upon the exposure of the xerogel to visible light irradiation, Scheme 1a.The • OH radical first attacked the MB dye to produce F1 fragment (4aH-phenothiazine, m/z = 199) which upon further attack by • OH radical produced diols fragment F2 (2H-1,4-benzothiazine-2,3-diol, m/z = 181) and F3 (benzene-1,2-diol, m/z = 110).The final product obtained was prop-2-enal in case of MB dye.For ARS dye, Scheme 1(b), the attack of • OH radical on the side chain of the sulphur of the anthracene parent compound formed F1 fragment (1-hydroxy-4a,9a-dihydroanthracene-9,10-dione, m/z = 226).The F1 fragment further degraded to F2 fragment, eliminating all the oxygen molecules on the surface of the parent compound.This is followed degradation of the aromatic rings, and the formation of acidic compounds.The fragment F2 degraded

ARS dye
ZnO nanoparticles [ 51] UV light 25 ppm 90 min 77% TiO 2 -doped Be (1%) [ 52] Visible light 10 ppm 90 min 82% Co-Mn NPs (15 wt%) [ 53] Visible light 200 ppm 150 min 83% 1-ZnO-poly(1-naphthylamine) nanohybrids [ 54] Microwave induced 200 pm 40 min 85% to F3 ( m/z = 146) which further formed F4, F5, and the final product obtained was butan-1-ol.Similarly, for RhB and MO dyes, Scheme 1c,d, the major fragments were substituted aromatic rings which were formed due to the attack of • OH radical.The final fragments generated were small molecules and hence reflect the highly efficient degradation of the dyes using these xerogels.The comparative data on the photocatalysts used for the degradation of dyes, Table 1 shows that our xerogels were more effective than inorganic photocatalysts in degrading the dyes.Vidya et al. [43] reported the photocatalytic ability of PANi-NiO nanocomposite via MB dye degradation under visible light irradiation.Almost 76% of 10 ppm MB dye degraded in 300 min.Punnakkal et al. [44] showed that 10 wt% Ag/PPy degraded 90% of 5 ppm MB dye in 180 min, while Rahman et al. [45] studied the degradation of MB dye under UV light using PANI-TiO 2 and confirmed that 86.35% of MB dye degradation was achieved in 90 min using 10 ppm of the dye solution.Likewise, Zhang et al. [46] carried out the degradation of 50 ppm MB dye using reduced graphene/Fe 2 O 3 /PPy hydrogel and showed 100% degradation in 80 min.Mandal et al. [47] showed 90.78 % MB dye degradation in 130 min.Tantawy et al. [48] reported bimetallic solid comprised of Ag and Cu nanoparticles (Ag─Cu NPs) which revealed 70% MB dye degradation in presence of oxidizing and reducing agents at room temperature, whereas Elshypany et al. [49] and Nada et al. [50] studied the visible light-induced MB dye degradation using Fe 3 O 4 /ZnO and ZnFe 2 O 4 @TiO 2 respectively which exhibited 88.5% and 98% degradation in 160 and 180 min respectively.Zn nanoparticles were utilized by Kansal et al. [51] for the degradation of ARS dye which showed 77% degradation in 90 min.TiO 2 -doped Be revealed 82% degradation of ARS dye in 90 min, while Co-Mn degraded 83% of the ARS dye in 150 min. [52,53]Our previous studies on ARS dye degradation via microwave irradiation revealed 85% degradation of 200 ppm ARS dye in 40 min.The xerogel reported in this study revealed 91% and 88%, for MB and RhB dyes, while ARS and MO dyes show 96% and 92% degradation which was comparable (and superior in some cases) to the photocatalytic degradation using metallic nanoparticles as catalysts.

Conclusion
Composite xerogels based on conducting polymers were successfully synthesized using chemical oxidative polymerization and were characterized for their spectral, optical, thermal, and morphological properties.Visible light-induced photocatalytic properties of the synthesized xerogels were examined for ARS, MB, RhB, and MO dyes.The kinetics of photocatalytic degradation followed the first-order model and was found to be highest for PANI/PPy-2/1 composite xerogel revealing 91% degradation of MB dye solution in 120 min.For ARS dye solution, the degradation was 96% in 90 min.The recyclability test confirmed that the catalysts could be used safely for up to 6 cycles.Thus, composite xerogels with optimum loading of conducting polymers can be used as efficient photocatalysts for the degradation of toxic environmental pollutants.
Synthesis of Pristine PANI and PPy Xerogels: The synthesis of PANI xerogel was carried out using aniline (1 mmol) and phytic acid (1 ml) which were dissolved in distilled water (5 ml) keeping the molar ratio of aniline:phytic acid as 1:5.Ferric chloride (1 g) was dissolved in 2.5 ml distilled water keeping the molar ratio of oxidant: monomer as 2:1.Both solutions were cooled to 2 °C separately and were then mixed immediately.The gelation was observed after 4-5 min accompanied by a change in the color of the solution from brown to green.The obtained xerogel was left undisturbed for 24 h and then centrifuged with distilled water and ethanol so as to remove any unwanted/unreactive impurities.The obtained xerogel was then freeze-dried.In a similar manner, polypyrrole (PPy) xerogel was also synthesized.
Synthesis of PANI/PPy Composite Xerogels: Aniline (1.1 ml) and pyrrole (1.05 ml) monomers were added in a 50 ml flask containing phytic acid (1.25 ml) and ethanol (5 ml).The solution was stirred on a magnetic stirrer for 2 h on an ice bath.In a separate beaker, FeCl 3 was dissolved in 2.5 ml distilled water.The temperature was lowered to 2 °C and the solutions were mixed rapidly.Gel formation occurred within 5 min.The obtained gel was freeze-dried for 24 h.After 24 h, the xerogel was centrifuged with distilled water so as to remove unwanted/unreactive impurities.A series of PANI/PPy xerogels with different molar ratios of aniline pyrrole1:1, 2:1, 1:2 were synthesized and designated as PANI/PPy-1/2, PANI/PPy-1/1, and PANI/PPy-2/1.
Characterization -Morphological Analysis: Field emission-scanning electron microscopy (FE-SEM) (Leo Supra 50 V P, Carl Zeiss, Germany) was used to analyze the morphology.XRD was recorded on Rigaku, Ultima, Diffractometer (Japan) instrument using Cu-K radiation.
Spectral Analysis: The FTIR analysis of the gels were carried out on FTIR spectrophotometer (Perkin Elmer, USA).The dried gels were mixed with KBr powder to form pellets.The UV spectra of the samples were taken on UV-vis spectrophotometer model Shimadzu UV-1800 with DMSO as solvent.
DLS Studies: DLS measurements were performed using a ZetaSizer Nano-ZS (Malvern Instruments) (Zetasizer Nano user manual 2013).Each sample was loaded into a disposable micro cuvette and measured at 25 °C.
Thermal Analysis: TGAs were performed using a Mettler Toledo Thermal Analysis TGA/DSC 2 with a STARe Software System.In each analysis, the sample was placed in an appropriate crucible, which was then heated from 25 to 800 °C, at a heating rate of 10 °C min −1 under nitrogen (N 2 ) as a flow gas.
Photocatalytic Activity: Degradation of Azo dyes was conducted in presence of halogen lamp.The composite xerogels were used in the concentration range of 50-100 mg and were dispersed in the dye solutions of Methylene blue (MB), Alizarin Red S (ARS), Methyl Orange (MO), and Rhodamine B (RhB) (250 ml).The solution was sonicated for 30 min.The adsorption-desorption equilibrium between the dye solutions and catalyst was established by keeping the suspension in the dark.ARS dye solution was exposed to visible irradiation for 90 min, while that of MB dye was exposed for 120 min.RhB and MO dyes were exposed to 100 min.At regular intervals, aliquots of the solution (5 ml) were collected and the UV spectrum of the dyes was recorded against their reported max values. [28,29]cavenging Experiments for Analysis of Radical Generation: In order to determine the role of reactive species responsible for the degradation mechanism, radical generation experiments were carried out per the method reported in the previous studies. [30]5 mm of scavengerstert-butanol (TBA) and ethylene diamine tetra acetate (EDTA) were used for hole (h + ) detection and O 2 •− radical detection respectively.Scavengers were separately added to the dye solution (50 ppm) containing the catalyst (100 mg) in order to examine their effects on the rate of degradation.
Recyclability Tests: The reusability of synthesized xerogels were examined up to 6 cycles.Following the completion of each cycle, the xerogels samples were collected, regenerated, and dried for 7 h in a vacuum oven at 60 °C.The process was repeated 5 times, with the acquired catalysts reused in the following cycle.

Figure 8 .
Figure 8. a) Zeta potential of PANI/PPy-2/1 xerogel at different pH, b) Degradation percent of Methylene blue and alizarin red c) Degradation of RhB dye and and MO dye by PANI/PPy-2/1 xerogel at different pH.

Table 1 .
Comparative studies of degradation of MB and AR dyes using different catalyst.