FeOOH and nZVI combined with superconducting high gradient magnetic separation for the remediation of high-arsenic metallurgical wastewater

Metallurgical wastewater with high arsenic (As) concentration presents important challenges to human health and the environment because of its high toxicity and carcinogenicity. Iron (Fe)-based adsorbents can effectively detoxify low As-containing wastewater but are less helpful for high concentration of As and for solid–liquid separation. Herein, an advanced strategy is proposed to dispose high As wastewater using nano-zerovalent iron (nZVI) and ferric oxyhydroxide (FeOOH) combined with superconducting high gradient magnetic separation (HGMS) technology. The superconducting HGMS technology promoted the removal of As by nZVI and FeOOH via a magnetic flocculation reaction, while simultaneously separating reaction products adsorbed As from wastewater. Interestingly, nZVI could be corroded to release Fe(II) ions which then generated Fenton reaction under aerobic conditions, facilitating the oxidization of As(III)/Fe(II) to As(V)/Fe(III) ions. The Fe(II) and Fe(III) hydrolyzed in the form of hydroxy hydroxide and further generated the magnetic flocculates and coprecipitate. The results showed that 99.06% of As was successfully removed from wastewater with an initial As concentration of 5358 mg/L, at a dosage of 20 g/L, a magnetic field strength of 5 T, and a flow velocity of 500 mL/min. Compared with FeOOH, nZVI showed more favorable adaptability for lead smelting wastewater. Removal of As from wastewater by using nZVI combined with superconducting HGMS technology has a great potential to achieve industrial application for metallurgical heavy metal wastewater.