Search

The pollution of heavy metals and organic compounds has received increased attention in recent years. In the current study, a novel biochar-based iron oxide composite (FeYBC) was successfully synthesized using pomelo peel and ferric chloride solution through one-step process at moderate temperature. Results clearly demonstrate that FeYBC exhibited more efficient removal of Cr(VI) and/or phenol compared with the pristine biochar, and the maximum adsorption amounts of Cr(VI) and phenol by FeYBC could reach 24.37 and 39.32 mg g−1, respectively. A series of characterization data suggests that several iron oxides such as Fe 2 O 3 , Fe0, FeOOH and Fe 3 O 4 were formed on the FeYBC surface as well as oxygen-containing groups. Thermodynamics study indicates that Cr(VI) and phenol adsorption by FeYBC were endothermic and exothermic processes, respectively. Langmuir adsorption isotherm and pseudo-second order models could better explain the Cr(VI) and phenol adsorption behaviors over FeYBC. The Cr(VI) adsorption might be primarily achieved through the ion exchange and surface complexation and reduction, whereas the π–π interaction and electron donor–acceptor complex mainly contributed to phenol adsorption. The findings indicate that the biochar-based iron oxide composites material was an efficient adsorbent for the remediation of industrial effluents containing Cr(VI) and phenol. [Display omitted] • A novel biochar-based iron oxide composite (FeYBC) was firstly synthesized. • FeYBC exhibited more efficient Cr(VI) and phenol removal than pristine biochar. • Langmuir and pseudo second order models well explain Cr(VI) and phenol adsorption. • Cr(VI) and phenol adsorption were endothermic and exothermic nature, respectively. • The possible removal mechanism of both Cr(VI) and phenol adsorption was proposed. [ABSTRACT FROM AUTHOR]

Nowadays, nanoscale zero valent iron (nZVI) has been extensively applied for the decontamination of various pollutants, but passivation of nZVI severely affects its reactivity in use. In this study, ultrasound (US)-assisted catalytic reduction of Cr(VI) by an acid mine drainage based nZVI (AMD-nZVI) coupling with FeS 2 system was systematically examined. Results show that the presence of FeS 2 and US induced a synergistic enhancement of Cr(VI) removal by AMD-nZVI. Nearly 98% of Cr(VI) removal was achieved by AMD-nZVI/FeS 2 /US process within 60 min under optimal reaction conditions. Several coexisting substances with lower concentration including Pb(II), Ni(II), bisphenol A (BPA) and 2,4-diclorophenol (2,4-DCP) could be effectively removed in simultaneous manner with Cr(VI) removal. The inhibitory order of water matrix species on Cr(VI) removal was NO 3 − > PO 4 3− > HCO 3 − > Ca2+ > Mg2+ > Cl−, and a serious suppression effect was induced by humic acid (HA). Addition of ethylene diamine tetra-acetic acid (EDTA) and citric acid (CA) could enhance Cr(VI) removal rate. An enhanced reaction mechanism was proposed, which involved the regeneration of more Fe2+ and H+ by AMD-nZVI/FeS 2 /US process, leading to the reduction of Cr(VI) by AMD-nZVI and FeS 2 into Cr(III) species inculding Cr 2 O 3 and Cr(OH) 3. This study well demonstrates that AMD-nZVI/FeS 2 /US process is considered as a potential candidate for the remediation of Cr(VI) in real wasterwater. Image 1 • FeS 2 induced an enhanced removal of Cr(VI) by AMD-nZVI/US process. • The formation of Fe2+ and acidic condition played a primary role in this process. • Removal of Pb(II), Ni(II), 2,4-DCP and BPA could be achieved with Cr(VI) removal. • Most of Cr(VI) species was sucessfully reduced into Cr 2 O 3 and Cr(OH) 3. • Enhanced mechanism of Cr(VI) removal by AMD-nZVI/FeS 2 /US process was proposed. [ABSTRACT FROM AUTHOR]