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The main objective of this study is to optimize a new composite for the depollution of contaminated water. The sodium hydroxide-modified avocado shells (NaOH-AS) were firstly prepared, characterized by field-emission-scanning-electron-microscopy (FE-SEM), X-ray energy dispersive spectroscopy (EDS) and Fourier transforms infrared (FT-IR) spectroscopy, and applied for efficient removal of crystal violet dye (CV) in wastewater. In addition, the adsorption in a batch system of CV dye on the NaOH-AS material was studied. Therefore, we accomplished a parametric study of the adsorption by studying the effect of several important parameters on the decolorizing power of the used material, namely, initial pH, contact time, initial CV dye concentration, temperature, and the ionic strength effect on the CV dye adsorption process were systematically assessed. The highest adsorption efficiency of CV dye (>96.9%) by NaOH-AS was obtained at pH >8. The pseudo-second-order kinetic model gave the best description of the adsorption kinetic of CV dye on the AS and NaOH-AS adsorbents. In addition, the mass transfer of CV dye molecules from the solution to the adsorbent surface occurred in three sequential stages (boundary layer diffusion, intraparticle diffusion and adsorption equilibrium). The adsorption isotherm data were best fitted with the Freundlich model. The adsorption capacity of AS increased from 135.88 to 179.80 mg g−1 after treatment by 1 M NaOH. The thermodynamic study showed that CV dye adsorption onto NaOH-AS was an exothermic and feasible process. The electrostatic interactions acted as the only forces governing the CV adsorption mechanism. The NaOH-AS demonstrated a satisfactory reusability. Therefore, we can state that the as-developed NaOH-AS material has a potential application prospect as an efficient adsorbent for CV dye from wastewaters. HIGHLIGHTS NaOH-AS is an efficient adsorbent for removal of crystal violet dye from aqueous solutions.; Equilibrium data were well described by Freundlich isotherm model.; The maximum uptake capacity was found to be 179.80 mg/g.

In this work, the core–shell PANI@WO3 composite was obtained from the reaction of aniline monomer polymerization with WO3 particles; sodium persulfate was used as an oxidant. Various analytical techniques such as scanning electron microscopy (SEM-EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET), and X-ray photoelectron spectroscopy (XPS) were used to characterize the as-prepared PANI@WO3 adsorbent, which well confirmed that the WO3 particles were coated by polyaniline polymer. The PANI@WO3 composite was tested as an adsorbent to remove reactive orange G (OG) for the first time. pH, adsorbent dose, contact time, initial dye concentration, and temperature were systematically investigated in order to study their effect on the adsorption process. The experimental findings showed that the PANI@WO3 composite has considerable potential to remove an aqueous OG dye. Langmuir and Freundlich's models were used to analyze the equilibrium isotherms of OG dye adsorption on the PANI@WO3 composite. As a result, the best correlation of the experimental data was provided by the Langmuir model, and the maximum capacity of adsorption was 226.50 mg g 1. From a thermodynamic point of view, the OG dye adsorption process occurred spontaneously and endothermically. Importantly, PANI@WO3 still exhibited an excellent adsorption capability after four regeneration cycles, indicating the potential reusability of the PANI@WO3 composite. These results indicate that the as prepared PANI@WO3 composite could be employed as an efficient adsorbent and was much better than the parent material adsorption of OG dye

Herein, we report the preparation of a novel biosorbent; a citric acid modified red-seaweed for crystal violet (CV) removal from water. Surface characterization and basic biosorption characteristic...

The focus of the current research is to evaluate the adsorption mechanisms of sodium salicylate and metronidazole on the polyaniline (PANi) using density functional theory (DFT) at B3LYP/6-31G(d) level of theory. The molecular electrostatic potentials of sodium salicylate, metronidazole and PANi were calculated. The theoretical data show that the oxygenated functional groups of adsorbates and amino groups of PANi are the nucleophilic and electrophilic attack sites, respectively. The structural, electronic and energetic properties of PANi complexed with sodium salicylate and metronidazole were investigated. The adsorption mechanism is due to the formation of hydrogen bond between polymer and adsorbate molecules. The low intermolecular electron transfer at solute/solid interface reveals that the sodium salicylate and metronidazole are physisorbed onto the PANi. In addition, the interaction energies between PANi and adsorbate molecules suggest the stability of the formed complexes, indicating a good adsorbate-adsorbent affinity. All quantum chemical data are in good agreement with the experimental observations.

This work focuses on the removal of hemimellitic, trimellitic, and pyromellitic acids from aqueous solution using polyaniline-polypyrrole copolymer. The experimental data indicate that the adsorption is well described by the pseudo-second-order kinetic model and the Langmuir isotherm model. The maximum adsorbed quantities of hemimellitic, trimellitic, and pyromellitic acids are 79.94, 93.55, and 111.29 mg/g, respectively. The thermodynamic study shows that the adsorption was a spontaneous and endothermic process. The adsorption mechanism was investigated using the density functional theory (DFT) at the B3LYP/6-31G(d). The theoretical data show that the adsorbate molecules were physisorbed via their carboxylic groups on the hydrogen atoms in amine groups of the polyaniline-polypyrrole. All the results suggest that the PANi-PPy copolymer is an efficient recyclable adsorbent for wastewater treatment.

Synthetic dye waste is one of the world's key ecological concerns. The algal biomass has emerged as a promising alternative adsorbent for wastewater treatment. The present study deals with the functionalization of brown algae (BA) by citric acid in order to improve its adsorption ability for textile dye removal in aqueous solutions. The morphological texture (SEM and BET) and surface chemistry (FTIR, EDS-mapping, and PZC) of the novel functionalized brown algae (designated as BA-CA) were analyzed. The performance of BA-CA for crystal violet (CV) dye removal from wastewater was investigated. The isotherm and kinetic adsorption modeling indicate the good fit of Langmuir isotherm and pseudo-second-order models. Optimum monolayer uptake capacity was 279.14 mg/g for BA-CA, which was about two times higher than that of unmodified BA. The thermodynamic parameters clearly indicated that CV removal process was physiosorption, exothermic, and spontaneous in nature. The regeneration study showed excellent reusability of the BA-CA up to five cycles. Overall, the experimental findings lead us to conclude that the BA-CA can be used as an eco-friendly, cost-effective and easily regenerated adsorbent for the purification of textile effluents.

A novel polyaniline@Almond shell (PANI@AS) biocomposite was synthesized via facile in situ chemical polymerization method. The as-synthesized adsorbent was characterized using various analytical techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), and potentiometric titration. A batch adsorption system was applied with the aim of investigating as-synthesized adsorbent ability to remove Cr(VI) ions and Orange G (OG) textile dye from aqueous solutions. Obtained results revealed that adsorption process was strongly depended upon the physicochemical parameters. The adsorption of Cr(VI) and OG dye onto PANI@AS was better described by the pseudo second-order-kinetic model and followed the Freundlich isotherm model. The maximum uptakes were 335.25 for Cr(VI) and 190.98 mg g−1 for OG dye. We further evaluated that PANI@AS biocomposite could be regenerated easily with NaOH solution and efficiently reused for Cr(VI) and OG dye removal from aqueous media. Thus, these results indicated the potential practical application of PANI@AS biocomposite for wastewater treatment.

Present study reports the synthesis of the polyaniline-polypyrrole (PPY-PANi) copolymer and its subsequent application for aqueous metronidazole removal under batch adsorption trials. The experiments were then performed to determine the influence of different adsorption parameters such as adsorbent dose, pH, reaction time, initial concentration and temperature on the adsorption process. The obtained experimental data was further evaluated by using different kinetic, isotherm and thermodynamic modeling. The pseudo-first order model provided the satisfactorily explanation for metronidazole kinetic adsorption over PPY-PANi adsorbent. The equilibrium experimental data was in good agreement with Freundlich model. The thermodynamic parameters reveal that the adsorption was spontaneous and exothermic in nature. Metronidazole adsorption mechanism over PPY-PANi surface sites was further evaluated by employing density functional theory (DFT) method. The calculated data indicated that the metronidazole adsorption was mainly accomplished via nucleophilic groups (containing oxygen atoms) of metronidazole over the electrophilic attack sites (-NH-) of PPY-PANi adsorbent. The interaction energy bond clearly suggests that the adsorption of metronidazole over PPY-PANi is a physisorption in nature. Thus, based on these above-mentioned experimental results and DFT data, we concluded that PPY-PANi copolymer could be taken as an alternative filter material for pharmaceutical contaminated wastewater treatment.

The polyaniline coated with an agricultural waste (Argan nut shell) was prepared via in-situ chemical polymerization and used as an adsorbent material for removal of trimellitic (Tri), hemimellitic (Hemi) and pyromellitic (Pyro) acids from water in single and multi-component systems. The obtained results indicate that the adsorption process was strongly influenced by experimental parameters. The greatest adsorption efficiency was obtained at pH 6, adsorbent dose = 0.5 g/L, T = 25 °C, contact time = 90 min and initial concentration of 20 mg/L. The experimental data for single component systems fitted very well to pseudo-second-order kinetic model (R2 = 0.999). The intraparticle diffusion model suggests that the adsorption of Tri, Hemi and Pyro acids takes place in two successive stages representing the progressive adsorption and equilibrium. The single component adsorption equilibrium data were successfully described by the Langmuir isotherm model (R2 ≥ 0.995). The maximum monolayer adsorption capacity of polyaniline/Argan-nut-shell composite was found to be 209.64, 143.68 and 267.38 mg/g for Tri, Hemi and Pyro acids, respectively. In binary and ternary systems, the competitive behavior of the adsorption process was successfully predicted by an extended Langmuir isotherm model, with interaction parameters obtained from measured single data. Furthermore, the values of thermodynamic parameters (ΔH° ˃ 0, ΔS° ˃ 0 and ΔG ˂ 0) indicate that the adsorption processes were spontaneous, endothermic and physisorption in nature.