Fabrication of Nano-bentonite-Based Organo-minerals Composites of Biochar: Characterization and Application to Remove Arsenate from Contaminated Water

摘要

In this study, date palm waste-derived bio-char (BC) was modified through intercalation of nano-sized bentonite clay to fabricate organo-mineral composites. The BCs produced at 400℃ (BC4) and 600℃ (BC6) were loaded with 10 (BC4-10 and BC6-10) and 20 (BC4-20 and BC6-20) of nano-bentonite to synthesize composite materials, and then characterized using SEM., FTIR, BET, and CHNS analyzer, as well as proximate, and chemical analyses. The efficiency of the synthesized materials to remove arsenate (As(Ⅴ)) from contaminated aqueous media was explored through batch-type sorption trials. The results revealed that pH 5.5 was optimum for the maximum As(Ⅴ) removal. As(Ⅴ) sorption data was simulated with kinetics and isotherm sorption models to understand As(Ⅴ) removal process. The sorption data showed the best fitness with the pseudo-second-order kinetic model, followed by Elovich, suggesting a chemisorption mechanism. The intraparticle diffusion model predicted that apparent diffusion constant was the highest for BC6-20 (0.158 (mg g~(-1) min~(-1))~(-0.5)). The As(Ⅴ) sorption data was described well with Langmuir isotherm, followed by Temkin, Freundlich, and Dubinin-Radushkevich isotherm models. The maximum sorption capacity as predicted by Langmuir isotherm was the highest for BC6-20 (7.48 mg g~(-1)), followed by BC4-20, BC6, BC6-10, BC4-10, BC4 (7.19, 6.75, 6.23, 6.20, and 5.81 mg g~(-1), respectively). Kinetics and isotherm modeling data as well as results of post-sorption FTIR analyses suggested that multiple mechanisms were involved in the removal of As(Ⅴ) such as electrostatic interactions, chemisorption (monolayer and multilayer sorption) and intraparticle diffusion. Overall, composites of BC with 20 nano-sized bentonite removed up to 191 more As(Ⅴ) from aqueous solution than pristine materials. Therefore, nano-bentonite based organo-minerals composites of BC could be used as an efficient, environment-friendly, and cheaper technology to decontaminate As(Ⅴ)-contaminated water.