An improved preparation method of carbon aerogels derived from alginate/chitosan with a superiority of promoting nZVI for chromium(VI) ions removal from aqueous solution

CAs (carbon aerogels) are potential novel adsorbents for Cr(VI). However, their tradition preparation method presents a series of problems such as the tedious processes and the limited scaling up production caused by extreme conditions. Improved preparation methods are tried to explore so that supercritical process could be avoided. While the explanation of the adsorption behavior and mechanism remain incomplete in the presence of polyanions. In this paper, a series of sodium alginate/chitosan composite (SA/CTS) carbon aerogels with or without nZVI (nano zero-valent iron) doped are intentionally designed, which were prepared without super-critical process and expected to a significant improvement in Cr(VI) removal in wastewater while facilitating preparation and separation. The adsorption performance of carbon aerogels for Cr(VI) were investigated as functions of pH, adsorbent dosage and adsorption temperature. Following the study of adsorption behavior of Cr (VI) in the coexistence of polyanions, this work presented a detailed rationale for the different competing anions having different effects on Cr(VI) sorption. Four isotherms and three kinetic models were used to explain the adsorption behaviors. The maximum adsorption capacities of CTS900 and nZVI@CTS900 were estimated to be 183.85 mg/g and 204.35 mg/g at 35 degrees C using the Sips model, respectively, which showed favorable performance over carbon aerogel materials that have been reported so far. Besides the study of factors influencing adsorption, the mechanism of Cr(VI) sorption mainly involved electrostatic interactions, hydrogen bonding attraction, and redox reactions were demonstrated through the multi characteristic analysis. As a result, prepared CTSs and nZVI@CTSs perform acceptable application prospects in Cr(VI)-containing water and wastewater.

Automated summary

In this paper, a series of SA/CTS composite carbon aerogels were designed and prepared without supercritical process, aiming to improve the removal efficiency of Cr(VI) in wastewater. The adsorption performance of carbon aerogels for Cr(VI) and the mechanisms involved were studied. The prepared CTSs and nZVI@CTSs showed promising prospects for application in Cr(VI)-containing water and wastewater.