Mechanistic view of MoS2 confined chitosan-polyaniline hybrid composite for the photo-oxidation of cationic dyes.

In this article, we describe the formulation of polyaniline-chitosan/MoS2 (PANI-CS @MoS2) blended composite and evaluated its efficiency to degrade the dye molecules Rhodamine B (RhB) and Malachite Green (MG) under visible light. In the photocatalytic mechanism, the CS acts as an electron carrier and binding agent during the oxidation reaction to decrease the recombination of electrons and holes generated by the irradiation of light. FTIR, XPS, XRD, TG, Zeta Potential, UV, SEM, AFM and TEM were used to characterize the PANI-CS@MoS2 composite after it had been synthesized. For the degradation analysis, 30 mg/L concentrations of 50 mL MG and RhB dye solutions were used. The recommended dosage of the composite was 100 mg. For MG and RhB dyes, the colour removal rates were 96.2 % and 91.5 %, respectively, under exposure to visible light and at the pH ranges of 8-11. After being exposed to visible light for 60 min, the whole decay process was accomplished. The photocatalyst offers great extensibility up to five iterations. The Langmuir-Hinshelwood kinetic model governs the rate of dye molecules degradation. The result of the study revealed that the PANI-CS@MoS2 composite matrix perhaps be a trustworthy and practical substrate for the efficient refinement of dye-deteriorated water⁠⁠⁠⁠⁠⁠⁠.

Complex interior and surface modified alginate reinforced reduced graphene oxide-hydroxyapatite hybrids: Removal of toxic azo dyes from the aqueous solution.

In this study, alginate reinforced reduced graphene oxide@hydroxyapatite (rGO@HAP-Alg) hybrids have been fabricated via co-precipitation technique. The developed adsorbent was effectively utilized for the removal of Reactive Blue 4 (RB4), Indigo Carmine (IC) and Acid Blue 158 (AB158) azo dyes from aqueous solution, and found to have the adsorption efficiency of 45.56, 47.16 and 48.26 mg/g, respectively. The thermodynamic parameters demonstrated the endothermic and spontaneous nature of the adsorption process. The adsorption system was pH-dependent and showed maximum dye removal at pH 6-7, which was indicative of the electrostatic interactions, surface complexation and the hydrogen bonding mechanisms involved between the adsorbate and adsorbent during the adsorption process. Furthermore, the renewability studies demonstrated the reusability and stability of rGO@HAP-Alg hybrids up to five successive cycles. This study delivers a promising strategy for removing dye molecules and extends the potential application of rGO@HAP-Alg hybrids to treat practical dye contaminated water/wastewater.

Environment responsive Al3+ networked chitosan-gelatin spherical beads for the effective removal of organic pollutants from aqueous solutions.

In order to remove noxious Congo Red (CR), Acid Red 1 (AR1) and Reactive Red 2 (RR2) dye molecules from water, an environment responsive and biodegradable spherical chitosan-gelatin biopolymeric beads were designed and embedded with Al3+ ions. The surface morphology, specific surface area, crystalline phases, elemental composition and thermal properties of the CAG spherical beads had examined. Adsorption experiments were explored to investigate the adsorption properties of dye molecules on CAG spherical beads. The adsorption parameters like solution pH, contact time, co-existing ions, adsorbent dosage and regeneration studies were optimized using batch experiment method. The maximum adsorption efficiency of CR, AR1, and RR2 dye molecules on CAG spherical beads were 34.89, 32.36 and 33.63 mg/g, respectively. The adsorption system fits well with pseudo-second-order kinetics and Freundlich isotherm model. The molecular interactions followed in the adsorption mechanisms were the electrostatic force of attraction, surface complexation and hydrogen bondings that exist between dye molecules and the CAG spherical beads. The CAG spherical beads could be regenerated up to six consecutive cycles using an aqueous 0.1 M NaOH solution. The study emphasizes that the fabricated CAG spherical beads could act as a potential adsorbent in the water/wastewater treatment process.

Synthesis and characterization of La(III) supported carboxymethylcellulose-clay composite for toxic dyes removal: Evaluation of adsorption kinetics, isotherms and thermodynamics.

The discharge of organic dyes into the aquatic environment is a serious problem owing to the persistence of possible health risks and ecological hazards of these pollutants. This paper reports a facile method for the preparation of composite material consisting of lanthanum incorporated carboxymethylcellulose-bentonite (LCB) composite and utilized for the removal of Indigo Carmine (IC), Acid Blue 158 (AB158) and Reactive Blue 4 (RB4) dyes from water by batch adsorption techniques. The optimal conditions for the dye adsorption were found to be pH = 3, initial dye concentration: 50 mg/L and adsorbent dosage of 100 mg. The adsorption efficiency of IC, AB158 and RB4 dye molecules were 80.41%, 83.54% and 86.91% respectively. The entire adsorption process was completed within 40 min. The adsorption data fits well with the pseudo-second-order kinetic model, demonstrating the physico-chemical adsorption of the dyes on LCB matrix. The Langmuir, Freundlich, and D-R isotherm models were used to describe saturation point. The fabricated adsorbent material was characterized using PXRD, FTIR, SEM-EDAX, TGA-DSC and surface area measurements. The thermodynamic studies revealed that the adsorption was spontaneous and endothermic in nature. The LCB composite showed remarkable adsorption-desorption efficiency for dye removal in water/wastewater treatment process; hence it can be considered as a competent and potential adsorbent for dye removal.

Facile synthesis of chitosan-La3+-graphite composite and its influence in photocatalytic degradation of methylene blue.

Integrated photocatalytic composite adsorbents (IPCA) are used to degrade toxic organic and inorganic compounds in presence of UV/visible light irradiation. The compound preserves all the existing features of individual components and at the same time overcome drawbacks like rapid recombination of photogenerated electrons, low absorptivity and hindrance effect of the photocatalyst. Herein, an integrated Photocatalytic Chitosan-La3+-Graphite composite adsorbent was synthesized and the resultant composites were characterized by FTIR, XRD, TGA, EDX and SEM analysis. The UV-visible diffusion reflectance spectroscopy (UV-vis DRS) was used for the band gap measurement and it was found to be 3.2 eV. An aqueous solution of methylene blue (MB) dye (30 mL of 100 mg/L) was used to study the photocatalytic efficiency of the prepared IPCA. The Chitosan-La3+-Graphite Composite (CS-La-GR) (100 mg of dosage) exhibits enhanced photocatalytic degradation efficiency (93.5% in 40 min) for Methylene blue under UV light irradiation. The highest photodegradation was due to the stronger adsorption of MB dye on the surface of highly porous IPCA. Moreover, the reactive species, ·OH radical and O2·- radical ions play a major role in the photocatalytic degradation of Methylene blue over composite photocatalyst.