Adsorption of rhodamine B and Cr3+ ion onto graphene/chitosan composite

Abstract

Graphene and chitosan acted as the adsorbents for simulated wastewater with rhodamine B. The novel material produced by freeze-drying obviously outperformed graphene and chitosan in treating rhodamine B. Factors (e.g., contaminant concentration, reaction time, solution pH value, adsorption dose and temperature) overall impacted the adsorption. The optimal conditions for graphene-chitosan treatment of dyes included the concentration of pollutants at 400 mg/L, the dose of adsorbent as 5 mg, the solution pH at 4 and at 25∘C, and for 12 h, in which the maximal treatment amount reached 858.00 mg/g. The adsorption processes of Chitosan/graphene composites and magnetic Chitosan/graphene composites for simulated wastewater from Rhodamine B reactor followed Langmuir and Freundlich models, respectively. The in-particle diffusion model shows that the adsorption process of the composites for Rhodamine B simulated wastewater is not determined by either surface diffusion or in-particle diffusion. The magnetic Chitosan/graphene composites exhibit high recyclability, which can be respectively reused 3 times and 5 times and retain 80% adsorption capacity after being administrated with Rhodamine B simulated wastewater. By analyzing grey correlation degree, it is demonstrated that the concentration of pollutants and the reaction temperature critically affect the adsorption capacity. The electrochemical treatment with graphite rod for the Cr3+ was under the initial voltage of 30.6 V, at the pH of 5.59, and at the temperature of 18.5∘C; the removal rate of the samples was nearly 62.35% with the chromium ion concentration declined from 0.3333 g/L to 0.1255 g/L.