Highly Efficient Co-removal of Heavy Metals in Wastewater from Chemical Oxygen Demand Testing Instrument by Cysteine-functionalized Magnetic Nanoparticles

Wastewater discharged from chemical oxygen demand(COD) testing instrument was generally difficult to treat due to its high content of heavy metals and very low pH. In this study, a kind of cysteine-functionalized magnetic nanoparticles(MNPs-Cys) was synthesized and used to treat the wastewater. The synthesized MNPs-Cys as the adsorbent for heavy metal removal from aqueous solutions were systematically investigated. The adsorption dynamic process fit the Langmuir isotherms well with a maximum adsorption capacity of 76.92 mg/g for Cu(Ⅱ). The adsorbent could be easily regenerated by 0.1 mol/L HNO₃, which exhibited a high adsorption performance within 10 cycles. This adsorbent, combined with a developed pretreatment approach, could make Cr(Ⅲ), Hg(Ⅱ) and Ag(Ⅰ) in the wastewater discharged from COD testing instrument effectively removed and the removal efficiency is more than 99%. This work gave a new insight into the design and synthesis of high-performance materials for treating wastewater with heavy metals.