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The removal of hazardous dyes from water by magnetic biosorbents has received a lot of interest in recent studies. This is because they are inexpensive and simple to separate from the solution phase. In this study, nano-magnetic Tamarindus indica fruit seed biochar was combined with iron to create a green nano-magnetic/ biochar (BC) composite (nM-BC). Compared to unmodified biochar, modified biochar composite significantly improved the ability to adsorb methyl blue (MB) and malachite green (MG). The Dubinin-Radushkevich, Scathard, Freundlich, Langmuir, and Temkin models were used to analyze the adsorption equilibrium data, and the Langmuir isotherm (R2 =0.952–0.995) provided a good match to the results. Saturated BC adsorption capacities for MB and MG were 3.055 mg/g and 5.577 mg/g, respectively, while nM-BC values for MB and MG were 3.326 mg/g and 20.408 mg/g, respectively. The adsorption process is accurately described by the pseudo-second-order kinetic model. BC and nM-BC both passed four reusability tests. Utilizing FT-IR and SEM instruments BC and nM-BC were characterized. The study demonstrates that biochar can be enhanced with nano-iron which has a potent ability to remove dyes utilizing a green manufacturing approach.

In the present study, a heterogeneous adsorbent material (HA) was used as an adsorbent for the removal of Cr(VI) from aqueous solutions at laboratory scale. Cr(VI) containing water was treated with heterogeneous adsorbent(HA).Chromium solutions of various initial concentrations were treated with adsorbent in batch mode experiments to investigate the adsorption characteristics of heterogeneous adsorbent (HA). Kinetics of adsorption of Cr(VI) ions on adsorbent was investigated by using pseudo first order and second order kinetic models. Removal processes were found to be governed by pseudo second order model. Intraparticle diffusion model was also analyzed for this system. Removal was found to be increased by increasing the temperature from 298 to 318 K which indicates the endothermic nature of the process. Various two parameter isotherm models viz. Langmuir, Freundlich, Elovich, Tempkin, Dubnin–Raduskevich (D–R), Harkin–Jura and BET isotherm were applied on resultant data for equilibrium modeling. It was observed that heterogeneous adsorbent (HA) particles were highly efficient for the removal of Cr(VI).