Efficient adsorption and reduction of Cr(VI) by a novel polyaniline modified magnetic iron-based waterworks sludge from aqueous solution

As a major solid waste from the waterworks, the iron-based waterworks sludge (IBWS) was currently disposed of in landfills or discharged into water body, causing land consumption and environment contamination. This work investigated a novel reclamation of IBWS to create a composite for aqueous Cr(VI) adsorption and reduction. IBWS was magnetized by calcination and further modified with polyaniline (PANI) to get PANI@MIBWS for enhanced adsorbent separation and Cr(VI) removal. After being characterized using advanced techniques, the composite was employed in aqueous Cr(VI) removal studies. PANI@MIBWS removed Cr(VI) in a pH-dependent manner, with the highest Cr(VI) removal at pH 2. The spontaneous and endothermic Cr(VI) elimination process by the composite was best explained by pseudo-second-order and Langmuir models. In the sequence of Cl-＜SO42-＜PO43-, increasing Cl-, SO42- and PO43- concentrations resulted in declining Cr(VI) elimination. Chemical, electrostatic adsorption, Cr(VI) reduction to Cr (III), and chelation were involved into the Cr(VI) removal from water by PANI@MIBWS. The study found that the novel composite was effective for Cr(VI)-bearing wastewater treatment and had easy regenerability and good reusability, providing not only a fresh insight into the sustainable and eco-friendly disposal of IBWS, but also useful information for Cr(VI)-bearing wastewater treatment.