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Magnetic green adsorbents have been gaining importance in wastewater treatment field due to their versatile properties. In this study, a novel magnetic green adsorbent Zinc Ferrite-Rice Husk Silica (ZFN-RHS) composite has been prepared by extracting silica from rice husk. ZFN-RHS is characterised using variety of techniques which includes FESEM, FT-IR, XRD, BET, pHzpc and EDS. Effect of various parameters like time, concentration, pH, adsorbent amount and temperature was assessed using the batch adsorption method to remove cationic dyes (Methylene Blue and Crystal Violet) from aqueous solution in single as well binary dye solutions. Results showed that Lagergren pseudo-second order kinetic model best fitted with the adsorption data indicating chemisorption. In adsorption isotherm study, Freundlich as well as Langmuir adsorption isotherms fitted better than other isotherms. Maximum adsorption capacities for removal of CV and MB dyes in this study have been found to be 138.8 and 84.8 mg/g respectively. From the positive values of ΔH°, it has been observed that the process of removal of MB and CV from aqueous solution using ZFN-RHS was endothermic in nature and the negative ΔG° values confirmed the spontaneous nature of the process. Regeneration studies were also conducted with significant outcomes in five cycles. The research study revealed that ZFN-RHS can be used as an adsorbent to remove other cationic dyes also. [ABSTRACT FROM AUTHOR]

In the present work, magnetic nickel ferrite (NiFe2O4) have been synthesised using low temperature combustion method and then modified with Cetyltrimethylammonium bromide (CTAB) to form a magnetic composite. Prepared composite (CTAB-NiFe2O4) was used as an adsorbent for removing brilliant green dye from aqueous solution. Adsorbent was investigated by using various techniques like Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy, energy-dispersive spectra, thermogravimetric analysis and pH of point zero charge. Different parameters such as effect of contact time, pH, adsorbent dose and initial dye concentration were studied for the adsorption of dye. The optimum values observed were 170 minutes equilibrium time at pH 6 and adsorbent dose 0.6 g. Various adsorption kinetic models such as pseudo first-order kinetic model, pseudo second-order kinetic model and Elovich model were used to determine the nature of adsorption. Pseudo second-order kinetic model fitted better with higher R2 value which indicated that the adsorption was chemical in nature. Langmuir isotherm was best fitted to experimental data for the adsorption of brilliant green dye with maximum adsorption capacity 'Qe' 250 mg/g. It revealed that the adsorption in this study takes place on homogenous surface and follows monolayer pattern. Therefore, for the removal of Brilliant green dye from wastewater using composite (CTAB-NiFe2O4) can be considered as an effective adsorbent. [ABSTRACT FROM AUTHOR]

In the present work, Zinc ferrite composites with Mango starch (MS) and carboxymethyl mango starch (CMMS) were synthesized for the removal of Ni (II) ions from aqueous solutions. Composites prepared were characterized by Fourier Transform Infrared (FTIR) Spectroscopy, X-Ray Diffraction (XRD) analysis, pH of point zero charge (pHzpc), Scanning Electron Microscopy (SEM), and BET. Batch adsorption technique was used to study effect of various parameters such as pH, adsorbent dose, contact time, concentration, and temperature for removal of Ni (II) ions from aqueous solutions. The optimum time, pH, adsorbent dose and temperature required for ZFN@ MS and ZFN@ CMMS in this study was 110 min., 7 & 8, 0.1 g and 308 K, respectively. Out of various adsorption isotherms, Freundlich isotherm model fitted best with adsorption data. Maximum adsorption capacity for removal of Ni (II) were found to be 65.3 and 208.3 mg/g, respectively by using Zinc ferrite@ MS and Zinc ferrite@ CMMS adsorbents. Lagergren Pseudo second order model best fitted with results which indicated that the process of adsorption was chemical in nature. The value of adsorption energy for ZFN@ MS was 50 kJ/mol and for ZFN@ CMMS, it was 31.62 kJ/mol. Thermodynamic study revealed that process was endothermic and non-spontaneous in nature. Regeneration studies were conducted for five cycles where Zinc ferrite@ MS showed 71% regeneration efficiency and Zinc ferrite@ CMMS showed 78% regeneration efficiency for nickel ion removal from aqueous solution. [ABSTRACT FROM AUTHOR]