Enhanced sorption of hexavalent chromium [Cr(VI)] from aqueous solutions by diluted sulfuric acid-assisted MgO-coated biochar composite. (October 2018)

• Record Type: Journal Article
• Authors: Xiao, Ran; Wang, Jim J.; Li, Ronghua; Park, Jonghwan; Meng, Yili; Zhou, Baoyue; Pensky, Scott; Zhang, Zengqiang
• Is Part Of: Chemosphere. Volume 208(2018)
• Page Start: 408
• Page End: 416
• Publication Date: 2018-10
• Subjects: Cr(VI) ions -- Sulfuric acid hydrolysis -- Sugarcane harvest residue -- MgO coated biochar composite -- Sorption; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2018.05.175
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: Metal oxide-Carbon composites have aroused great interesting towards specific anionic contaminants removal from the polluted environment. In this study, aiming at removing toxic chromate ion [Cr(VI)] from aqueous solutions, a novel approach was developed to produce surface-enhanced MgO-coated biochar adsorbent from sugarcane harvest residue (SHR). It was found that sulfuric acid hydrolysis and MgO-coating both facilitated the removal of Cr(VI) by biochars, and the maximum sorption capacities for the pristine biochar (SHR550 ), MgO-coated biochar (MgSHR550 ), and acid-assisted MgO-coated biochar (MgASHR550 ) that derived from the Langmuir isotherm model were 20.79, 54.64, and 62.89 mg g −1, respectively. Additionally, the Cr(VI) removal was a pseudo-second-order kinetic model controlled process with equilibrium reached within 24 h. The mechanism investigation revealed that Cr(VI) ions was directly sorbed by the MgO-coated biochars via the chemical interaction between MgO and Cr(VI), whereas the sorption-coupled reduction of Cr(VI) to Cr(III) governed the sorption of Cr(VI) on the SHR550 . Although the increases of solution pH (>2.0) and KNO3 concentration (>0.05 mol L −1 ) reduced the Cr(VI) removal by biochars, while there were lower secondary pollution risks in MgO-coated biochar treatments due to the suppressed release of Cr(III) in solutions. This work could provide guidance for the production of efficient biochar for the removal of Cr(VI) from wastewater. Graphical abstract: Image 1 Highlights: MgO coated biochar composite can effectively remove Cr(VI) from solutions. Acid pretreatment enhanced Cr(VI) removal by MgO coated biochar. Reduced secondary pollution risks [Cr(III)] in MgO-coated biochar treatments. 74.3% of sorbed Cr(VI) on MgASHR550 existed in the hexavalent oxidation state. MgSHR550 and MgASHR550 demonstrated high reusability.