Synthesis of magnetic chitosan biopolymeric spheres and their adsorption performances for PFOA and PFOS from aqueous environment.

Due to numerous applications and excellent environmental stability, long-chain perfluorinated chemicals (PFCs) are ubiquitous in water across the world and adversely affect the living organisms. Thus, this study focused on the mitigation of the most frequently used long-chain PFCs namely perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) from water using reduced graphene oxide modified zinc ferrite immobilized chitosan beads (rGO-ZF@CB) as an adsorbent. The results from the adsorption isotherm and kinetic studies revealed that the adsorption data fitted well to the Langmuir and the pseudo-second-order models. According to the Langmuir isotherm, the rGO-ZF@CB possessed the maximum adsorption capacity of 16.07 mg/g for PFOA and 21.64 mg/g for PFOS. Both the electrostatic attractions and hydrophobic interactions have driven the removal of PFOA and PFOS by prepared rGO-ZF@CB. Eventually, the rGO-ZF@CB could be considered as an efficient adsorbent for the effective removal of PFOA and PFOS molecules from the aqueous environment.

Facile synthesis of Zr4+ incorporated chitosan/gelatin composite for the sequestration of Chromium(VI) and fluoride from water.

The development of industrialization and agricultural activities have carried various negative impacts to living organisms in recent decades and also, the frequent problem of inorganic pollution have been environmental anxiety to the community. Among these, Cr6+ and F- are priority poisonous pollutants from many industries. In this work, we present a low-cost synthesis procedure to obtain biocompatible zirconium incorporated chitosan-gelatin composite (CS-Zr-GEL) were fabricated and explored for the adsorptive removal of toxic Cr6+ and F- from water. The adsorption mechanism of toxic Cr6+ and F- was done by batch mode as a function of contact time, solution pH and co-existing ions. The obtained materials were extensively studied by several physico-chemical techniques to access their properties by X-ray diffraction (XRD), scanning electron microscopy with Energy Dispersive X-ray Spectroscopy (SEM-EDX), Fourier-transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) analysis. Additionally, the fabricated adsorbent is highly dependent on solution pH. The kinetic and isotherm data were fitted using pseudo-second-order kinetic and Langmuir isotherm models. The maximum adsorption capacity for CS-Zr-GEL is 138.89 and 12.13 mg/g at 323K for Cr6+ and F- respectively. These findings demonstrate that the CS-Zr-GEL adsorbent represents a promising candidate that would have a practical influence on water/wastewater treatments.

Chitosan modified zirconium/zinc oxide as a visible light driven photocatalyst for the efficient reduction of hexavalent chromium.

Metal-sensitized biopolymeric hybrid materials can be strategically utilized in photo catalysis due to the behavior of their absorption band lying in the solar radiation spectrum. Herein, chitosan supported zirconium(Zr)/zinc oxide (ZnO)) in the preparation of photo catalyst (Zr-ZnO@CS) for photocatalytic reduction of hexavalent chromium(Cr6+). Moreover, photocatalytic testing factors like exposure time of light, pH, initial Cr6+ concentration, and influence of co-anions on the removal of Cr6+ by Zr-ZnO@CS were also examined. Langmuir-Hinshelwood kinetic model suggested the surface reaction was the rate-controlling step. The removal mechanism of Zr/ZnO@CS was because of enhanced properties like positive positioning of the band gap, boosted charge excitation, and higher dynamic sites. Field trial results showed that Zr-ZnO@CS hybrid photocatalyst demonstrates the potential application for the reduction of Cr6+ ions.

Enhanced photocatalytic response of ZnO embedded chitosan/ß-cyclodextrin towards the detoxification of Cr(VI) under visible light.

The present work focused on the assessment of heterogenous photocatalytic efficacy of ZnO@CS-ß-CD towards the degradation of hexavalent chromium under visible light illumination. The prepared ZnO@CS-ß-CD was extensively characterized using XRD, FTIR, SEM, EDX with mapping, TGA, DSC and UV/vis DRS techniques and the photoreduction of Cr(VI) to Cr(III) was confirmed by X-ray photoelectron spectroscopy. The DRS results revealed that the band gap of ZnO@CS-ß-CD was narrowed than ZnO from 3.23 to 2.01 eV. The photocatalyst hold excellent reusability up to seven cycles and the field trail results demonstrated for the practical application for the treatment of wastewater.

Removal of chlorpyrifos, an insecticide using metal free heterogeneous graphitic carbon nitride (g-C3N4) incorporated chitosan as catalyst: Photocatalytic and adsorption studies.

The present study investigates the photocatalytic degradation of an organic pesticide using a metal free heterogeneous graphitic carbon nitride (g-C3N4) incorporated into chitosan as catalyst. Chlorpyrifos (O, O-diethylO-3,5,6-trichloro-2-pyridyl phosphorothioate (CPFS)), an insecticide includes in a class of Organophosphate pesticides with a chemical formula (C9H11Cl3NO3PS). It is widely used in agricultural lands to control pests in cotton, fruit and vegetables. The acute toxicity of chlorpyrifos is still dangerous to all aquatic living organisms. The CS/g-C3N4 materials have been characterized using UV-vis spectrophotometer (UV-vis), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscope (SEM), Energy Dispersive X-ray Analysis (EDX), Thermal analysis (TGA-DSC), Chemical oxygen demand (COD), X-ray diffraction (XRD), Diffuse reflectance spectra (DRS) and Electron spin resonance (ESR). The degradation of pesticide using CS/g-C3N4 showed good efficiency of about 85%. The results suggest that CS/g-C3N4 composite is a good alternative for the treatment of chlorpyrifos in aqueous solution. We have proposed a novel photocatalyst by metal free heterogeneous graphitic carbon using melamine and its recombination effects were minimized by chitosan which act as an electron carrier. The enhanced photocatalytic performance could be attributed to an efficient separation of electron-hole pairs through a Z-scheme mechanism, in which chitosan acted as charge separation carriers.

Performance of chitosan engraved iron and lanthanum mixed oxyhydroxide for the detoxification of hexavalent chromium.

The iron - lanthanum mixed oxyhydroxide (FLMOH) and chitosan engraved iron - lanthanum mixed oxyhydroxide materials (CSFLMOH) were prepared successfully and utilized for the hexavalent chromium adsorption studies. The physicochemical properties of pristine and Cr(VI) treated adsorbents were characterized using XRD, FTIR, SEM with EDX, TGA and DSC analysis. The efficacy of the CSFLMOH was compared with FLMOH towards the uptake of Cr(VI) ions and was explored using batch technique under various influencing parameters viz., time, dose, pH, initial concentration and co-existing anions. Langmuir, Freundlich and Dubinin - Radushkevich isotherms were used to analyze the adsorption behavior at 303, 313 and 323 K. The rate of the reaction was calculated using reaction based and diffusion-based models. Recycle and reuse studies were demonstrated using 0.05 M NaOH as the desorbing medium.

Photo-reduction of Cr(VI) using chitosan supported zinc oxide materials.

Investigations were made in order to evaluate the photocatalytic reduction of hexavalent chromium (Cr(VI)) using zinc oxide (ZnO), zinc oxide impregnated chitosan beads (ZCB) and chitosan/zinc oxide composite (CZC) under UV light irradiation. The as-synthesized chitosan modified zinc oxide materials were characterized using FTIR, SEM, EDAX and EPR studies. Photocatalytic experiments were conducted to optimize various parameters viz., irradiation time, the amount of catalyst, pH, concentration of H2O2, light intensity, co-ions, initial concentration of Cr(VI) under UV irradiation. The maximum reduction percentage of Cr(VI) using ZCB and CZC under UV light was obtained at 60min of irradiation time. CZC possesses higher percentage of 99.8% Cr(VI) reduction compared to ZCB which in turn higher than ZnO under UV light irradiation. The kinetics of photo-reduction of Cr(VI) is explained on the basis of Langmuir-Hinshelwood mechanism. The kinetic studies demonstrated that the photocatalytic reactions followed the pseudo-first-order model. The reusability of as-synthesized ZCB and CZC was assessed. The Cr(VI) reduction by ZCB and CZC under UV light is governed by adsorption coupled photocatalytic reduction. The suitability of ZCB and CZC was checked by employing these catalysts with the effluent taken from a nearby industrial area using photocatalytic method.