Thirumalisamy Santhi

The current paper studies the preparation of a new tannin gel from Acacia nilotica for water purification and waste water remediation. Design of experiments is used for optimizing the tannin gel using tannin extract ( Taguchi method ) with formaldehyde in the assistance of microwave (TGAN) by the help of iodine number. The feasible combinations were tested in the removal of nickel from simulated and river water. In this study, the effect of adsorbent dosage, pH, and initial metal concentration on Ni (II) biosorption on modified Acacia nilotica tannin gel (TGAN) was investigated. Tannin gel was characterized by SEM, FTIR, XRD, and EDAX. The kinetic data was tested using pseudo‐first‐order, pseudo‐second‐order, and intraparticle diffusion model. The results suggested that the pseudo‐second‐order model ( R ² > 0.998) was the best choice among all the kinetic models describing the adsorption behavior of Ni (II) onto TGAN. Langmuir, Freundlich, Temkin, and Dubinin‐Radushkevich adsorption models were used to represent the equilibrium data. The best interpretation for the experimental data was given by the Langmuir isotherm and the maximum adsorption capacity 250 mg g ⁻¹ of Ni (II) was obtained at pH 5.04 at 296 K. Adsorption of Ni (II) onto TGAN is confirmed qualitatively by the use of atomic absorption spectroscopy. The BOD and COD values are considerably reduced after adsorption.

The use of cheap and eco-friendly adsorbents prepared from freely and abundantly available Acacia nilotica leaves for the removal of highly toxic Cr(VI) from aqueous solutions in single and binary ion solutions as well as from a mixture of it with Co(II) & Cu(II) was investigated by batch methods. The effects of pH, contact time, and initial metal ion concentration of Cr(VI) onto H2SO4-treated Acacia nilotica leaves (HAN) was investigated. The linear form of the Freundlich model achieved high coefficients of determination R2 = 0.9808 for Cr(VI) adsorption. The R2 values for fitting the adsorption rate data were greater than 0.983 for Cr(VI) ion, which indicates the applicability of pseudo-second-order kinetic model. The desorption and recycling ability of Cr(VI) and HAN were found to be good. The studies showed that this low-cost adsorbent could be used as an efficient adsorbent material for the removal of Cr(VI) from aqueous solutions.

The preparation of activated carbon (AC) from Ricinus communis leaves was investigated in this paper. Orthogonal array experimental design method was used to optimize the preparation of AC using microwave assisted zinc chloride. Optimized parameters were radiation power of 100 W, radiation time of 8 min, concentration of zinc chloride of 30% by volume, and impregnation time of 24 h, respectively. The surface characteristics of the AC prepared under optimized conditions were examined by pH_ZPC, SEM‐EDAX, XRD, and FTIR. Competitive adsorption of Ni²⁺ ions on Ricinus communis leaves by microwave assisted zinc chloride chemical activation (ZLRC) present in binary and ternary mixture was compared with the single metal solution. The effects of the presence of one metal ion on the adsorption of the other metal ion were investigated. The experimental results indicated that the uptake capacity of one metal ion was reduced by the presence of the other metal ion. The extent of adsorption capacity of the binary and ternary metal ions tested on ZLRC was low (48–69%) as compared to single metal ions. Comparisons with the biosorption of Ni²⁺ ions by the biomass of ZLRC in the binary (48.98–68.41%‐~Ni‐Cu and 69.76–66.29%‐~Ni‐Cr) and ternary solution (67.32–57.07%‐~Ni–Cu and Cr) could lead to the conclusion that biosorption of Ni²⁺ ions was reduced by the influence of Cu²⁺ and Cr³⁺ ions. The equilibrium data of the adsorption was well fitted to the Langmuir isotherm. The adsorption process follows the pseudo‐second‐order kinetic model.

The present paper aims to investigate the physical characteristics of Acacia nilotica leaves (MVM) relative to their use as an adsorbent for removal of hazardous Cr (VI) from waste water. The adsorbent was characterized by FTIR and SEM studies. The applicability of the Langmuir model to MVM was proved by the high coefficient of determination. Eight error analysis methods, namely, residual root mean square error (RMSE), chi‐square (χ²), sum of the square of the errors (ERRSQ), composite functional error (HYBRD), derivative of Marquardt′s percent standard deviation (MPSD), average relative error (ARE), sum of absolute error (EABS), and average percentage error (APE) were used to evaluate the suitability of the adsorption isotherm. Desorption reveals that recovery of the metal from adsorbent was possible. The ecofriendly adsorbent MVM is expected to be an environmentally and economically feasible adsorbent for the removal of Cr (VI) from aqueous solution and real waste water.

Removal of methyl red from aqueous solution by activated carbon prepared from the Annona squmosa seed by adsorption