Three dimensional BC/rGA aerogel:preparation,characterization,and adsorption of Cr(Ⅵ)

Graphene-based composite aerogel doped with other low-cost materials can reduce the cost and promote the use in water treatment.This work prepared ball-milled biochar/reduced graphene oxide aerogel(BC/rGA)using GO and low-cost ball-milled biochar(BC)in a certain proportion with the freeze-thawing technique and sol-gel method,and applied BC/rGA on the Cr(Ⅵ)removal from aquatic environments.The characterization results showed that aerogel had a honeycomb briquette three-dimension(3D)and mesoporous structure with interconnected pores,and proved the preparation progress of aerogel in principle.Compared with GO,rGA and BC/rGA had better adsorption performance with 3D structure and well-developed pores,and BC/rGA with the mixture ratio of BC and GO of 1:4 was more appropriate.The adsorption kinetics data of rGA and BC/rGA_((1:4))were fitting well with the pseudo-second-order model(R^(2)>0.951),and the isotherm adsorption results were fitting the Langmuir model well(R^(2)>0.974).The results demonstrated that the adsorption process was monolayer and endothermic adsorption involving chemisorp-tion.Additionally,the adsorption capacities of rGA and BC/rGA_((1:4))at solution pH 2 were 3.71 and 3.89 times greater than those at solution pH 8,respectively.High background ion strength and low temperature slightly inhibited the adsorption of Cr(Ⅵ)by both rGA and BC/rGA_((1:4)).The adsorption mechanisms of Cr(Ⅵ)on rGA and BC/rGA_((1:4))were electrostatic interaction,reduction and ion exchange.The use of BC/rGA could reduce the cost and promote the green reuse of agricultural waste.Overall,BC/rGA could be used as a promising green adsorbent alternative for the feasible treatment of heavy metal contaminated water.