Nanochitosan/carboxymethyl cellulose/TiO2 biocomposite for visible-light-induced photocatalytic degradation of crystal violet dye.

Development of novel bionanomaterials for water and wastewater treatment has gained increased attraction and attention in recent times. The present study reports an effective biocomposite-based nano-photocatalyst comprised of nanochitosan (NCS), carboxymethyl cellulose (CMC), and titanium dioxide (TiO2) synthesized by sol-gel technique. The as-prepared NCS/CMC/TiO2 photocatalyst was systematically characterized by X-ray diffraction, Fourier Transform Infrared spectroscopy, Scanning Electron Microscopy with energy dispersive X-beam spectroscopy, Differential scanning calorimetry (DSC), and Thermogravimetric analysis (TGA). Photocatalytic degradation of the crystal violet (CV) dye using this nano photocatalyst was studied by varying the irradiation time, catalyst dosage, feed pH, and initial dye concentration. Further, the kinetic analysis of dye degradation was explored using the Langmuir-Hinshelwood model, and a plausible photocatalytic mechanism was proposed. The modification of TiO2 using NCS and CMC accelerated photocurrent transport by increasing the number of photogenerated electrons and holes. Overall, the study indicated the excellent photocatalytic performance of 95% CV dye degradation by NCS/CMC/TiO2 than the bare inorganic TiO2 photocatalyst under visible light irradiation.

Phycoremediation for carbon neutrality and circular economy: Potential, trends, and challenges.

Phycoremediation is gaining attention not only as a pollutant mitigation approach but also as one of the most cost-effective paths to achieve carbon neutrality. When compared to conventional treatment methods, phycoremediation is highly effective in removing noxious substances from wastewater and is inexpensive, eco-friendly, abundantly available, and has many other advantages. The process results in valuable bioproducts and bioenergy sources combined with pollutants capture, sequestration, and utilization. In this review, microalgae-based phycoremediation of various wastewaters for carbon neutrality and circular economy is analyzed scientometrically. Different mechanisms for pollutants removal and resource recovery from wastewaters are explained. Further, critical parameters that influence the engineering design and phycoremediation performance are described. A comprehensive knowledge map highlighting the microalgae potential to treat a variety of industrial effluents is also presented. Finally, challenges and future prospects for industrial implementation of phycoremediation towards carbon neutrality coupled with circular economy are discussed.

Toxic heavy metal cadmium removal using chitosan and polypropylene based fiber composite.

The aim of the present work was to evaluate the performance of polypropylene (PP)/sisal fiber (SF)/banana fiber (BF) and chitosan-based hybrid (chitosan(CS)/SF)/BF) composite materials for the adsorptive removal of cadmium (Cd) ions from water waste. Polypropylene is harnessed for its importance in forming strong composite materials for various applications. Chitosan biopolymer encloses a great deal of amino and hydroxyl groups, which provide effective removal of Cd ions from wastewater. The batch adsorption studies proved that the removal of Cd ions was pH-dependent and attained optimum at pH 5.5 for both the composites. Langmuir and Freundlich models were applied for the obtained experimental values. Based on the R2 values, it was evidenced that the adsorption process was best fitted with the Freundlich isotherm than Langmuir. The sorption capacity of CS/SF/BF hybrid composite (Cmax = 419 mg/g) is higher than PP/SF/BF composite (Cmax = 304 mg/g), and allows multilayer adsorption. Kinetics studies revealed that the pseudo-second-order model was followed during the removal of Cd ion from wastewater. The overall evaluation proved that though both the adsorbents are suitable for the removal of Cd ions, the efficiency of CS-based ternary composite material is better than PP-based composite.

Removal of the heavy metal ion chromiuim(VI) using Chitosan and Alginate nanocomposites.

Removal of heavy metals from wastewater is essential to avoid water pollution. In the present study, the performance of Chitosan and Alginate nanocomposites was evaluated for the removal of chromium (VI) from water waste. The physicochemically characterized (FT-IR, XRD, SEM, DSC, and DLS) for wastewater treatment were studied. Batch adsorption experiments were performed to examine the removal process under various factors like the effects of initial concentration, adsorbent dose, pH, and agitation time. The metal ion removal was pH dependent and reached optimum at pH 5.0. Experimental data were analyzed by Langmuir and Freundlich adsorption isotherms. The isotherm study revealed that the adsorption equilibrium is well-fitted to the Freundlich isotherm and the sorption capacity of Chitosan and Alginate nanocomposites is very high, and the adsorbent favors multilayer adsorption. Pseudo-first- and -second-order kinetics models were used for describing kinetic data. It was determined that removal of Cr (VI) be well-fitted by second-order reaction kinetics. From the results, it was concluded that Chitosan and Alginate Nanocomposites is an excellent material as a biosorbent for Cr(VI) from water waste.

Adsorption and kinetic studies on the removal of chromium and copper onto Chitosan-g-maliec anhydride-g-ethylene dimethacrylate.

The present work was designed to remove toxic metals chromium and copper using the double grafted copolymer Chitosan-g-Maleic anhydride-g-ethylene dimethacrylate. The graft copolymer was synthesized through chain polymerization reaction using ceric ammonium nitrate as the initiator. Prepared Chitosan-g-Maleic anhydride-g-ethylene dimethacrylate was used in order to remove the heavy metals chromium and copper from aqueous solutions of 200ppm/L concentration proceeding batch adsorption process by varying the parameters such as adsorbent dose, contact time, pH and initial concentration of the metal solution. The experimental data were equipped with isotherm models such as Langmuir and Freundlich and pseudo-first order and pseudo-second order kinetics. The calculated results revealed that the adsorption favours Freundlich isotherm and follows pseudo-second order kinetics.

Adsorptive removal of copper (II) and lead (II) using chitosan-g-maleic anhydride-g-methacrylic acid copolymer.

In the present work, the maleic anhydride and methacrylic acid monomers were grafted one after another onto chitosan by using ceric ammonium nitrate as the initiator. The optimum conditions for grafting were studied by varying the initiator concentration, monomer concentration and reaction temperature. The synthesized grafted samples were subjected to various analytical techniques such as FTIR, XRD, TGA and DSC methods The proof of formation of graft copolymer was ascertained from the results of FTIR analysis and XRD studies. The TGA and DSC results conclude the highly thermally stable behavior of the prepared graft copolymer sample. The prepared graft copolymer was utilized for removing copper and lead from aqueous solutions and optimum adsorption parameters were evaluated under various pH, adsorbent dose, contact time and initial metal ion concentration. The adsorption and kinetic studies have been explained by Langmuir, Freundlich and pseudo - first order, second order and intra particle diffusion models. From the results, it was seen that Freundlich isotherm was best fit in the case of adsorption studies which followed pseudo second order kinetics. The obtained results showed that the chitosan-g-maleic anhydride-g-methacrylic acid copolymer was very efficient in removing the heavy metals copper and lead from aqueous solution.

Sorption studies on Cr (VI) removal from aqueous solution using cellulose grafted with acrylonitrile monomer.

Graft copolymerization of acrylonitrile on to cellulosic material derived from sisal fiber can be initiated effectively with ceric ammonium nitrate. The grafting conditions were optimized by changing the concentration of initiator and monomer. The change in crystallinity of the grafted polymeric samples was concluded from the XRD patterns. The prepared cellulose grafted acrylonitrile copolymer was used as an adsorbent to remove Cr (VI) ions from aqueous solutions. The efficiency of the adsorbent was identified from the variation in the percentage of adsorption with contact time, adsorbent dose and pH. From the observed results it was evident that the adsorption of metal ions increases with the increase in contact time and metal ion concentration. An optimum pH was found to be 5.0 for the removal of Cr (VI) from the aqueous solution. The results of the Langmuir, Freundlich, and pseudo first- and second-order studies revealed that the adsorption was found to fit well with Freundlich isotherm and follows pseudo second-order kinetics. From the above results, it was concluded that the cellulose-g-acrylonitrile copolymer was found to be an efficient adsorbent for the removal of Cr (VI) from aqueous waste generated from industries.

Sorption studies of lead (II) onto crosslinked and non crosslinked biopolymeric blends.

The removal of Pb (II) ions from aqueous solution by crosslinked (glutaraldehyde-chitosan/Nylon6/Polyurethane foam) and non crosslinked (chitosan/Nylon6/Polyurethane foam) blends has been investigated. Chitosan solution was blended with Nylon6 and Polyurethane foam in the ratio of 2:1:1 with and without crosslinking agent (glutaraldehyde), in order to obtain sorbents that are insoluble in aqueous acidic and basic solution. Batch adsorption studies were performed as a function of pH, contact time and adsorbent dose. The optimum pH required for maximum adsorption of lead was found to be 5. The equilibrium adsorption data has been tested for the Langmuir, Freundlich and Temkin isotherms. The data were suitable to Freundlich isotherm model for both the blends. The kinetic parameters of the adsorption process were estimated using the pseudo-first and pseudo-second order models. These data indicated that the adsorption process followed the pseudo-first-order kinetics.

Sorption studies on heavy metal removal using chitin/bentonite biocomposite.

Contamination of water by toxic heavy metals due to urbanization is a world-wide environmental problem, which changes chemical and biological properties of both surface and ground water. The heavy metals render the water unsuitable for drinking and are also highly toxic to human beings. Removal of heavy metals is therefore essential. Thus, in my present work batch adsorption studies have been used to remove the Cr(VI) from aqueous solution using chitin composite. The data obtained from batch method at optimized conditions have been subjected to Freundlich and Langmuir isotherm studies. The data were suitable for both models indicating favorability.

Removal of Cu(II) and Ni(II) using cellulose extracted from sisal fiber and cellulose-g-acrylic acid copolymer.

The extraction of cellulose from sisal fiber was done initially using the steam explosion method. The batch adsorption studies were conducted using the cellulose extracted from the sisal fiber and cellulose-g-acrylic acid as an adsorbent for the removal of Cu(II) and Ni(II) metal ions from aqueous solution. The effect of sorbent amount, agitation period and pH of solution that influence sorption capacity were investigated. From the observed results, it was evident that the adsorption of metal ions increases with the increase in contact time and adsorbent dosage. The optimum pH was found to be 5.0 for the removal of copper(II) and nickel(II) for both the extracted cellulose and cellulose-g-acrylic acid copolymer. The adsorption data were modeled using Langmuir and Freundlich isotherms. The experimental results of the Langmuir, Freundlich isotherms revealed that the adsorption of Cu(II) and nickel(II) ion onto cellulose extracted from the sisal fiber and cellulose-g-acrylic acid copolymer was found to fit well with Freundlich isotherm. The kinetics studies show that the adsorption follows the pseudo-second-order kinetics. From the above results, it was concluded that the cellulose-g-acrylic acid copolymer was found to be an efficient adsorbent.