Treatment of As-contaminated drinking water using a nano zero-valent iron/copper slag nanocomposite

Arsenite (As(III)) is one of the most toxic contaminants in surface and underground waters that needs to be removed from aquatic environments as it has harmful effects on human health and other living organisms. In this study, copper slag supported nanoscale zero-valent iron (nZVI/copper slag) adsorbent is used to reduce the concentration of As(III) from an aqueous environment up to a permissible level. nZVI/copper slag adsorbent was prepared using Fe3+ reduction by BH-. FE-SEM, EDX, XRD, FTIR, BET, VSM, and Zeta potential were utilized for characterization of the adsorbent synthesis. In this study, effective parameters on the As(III) removal were made into a function of initial concentration, adsorbent dosage, and pH of the solution at a constant time of 5 min using Design-Expert software. The results of experiments showed that only 7.9 g/L of nZVI/copper slag adsorbent in 5 min and pH of 5.4 can remove >99 % of As(III) with the initial concentration of 20 mg/L in aqueous solution. Among different isotherms, the Langmuir model with a maximum adsorption capacity of 4.27 mg/g could describe As(III) adsorption model. In addition, it was found that adsorption followed the pseudo-second order kinetics model. The amount of iron (Fe) leached from the adsorbent surface of nZVI/copper slag has been significantly reduced by using pure copper slag as a substrate in 3 consecutive cycles. Furthermore, nZVI/copper slag adsorbent can be separated from aqueous media by applying an external magnetic field due to its magnetic properties and high weight of pure copper slag.

Automated summary

In this study, a copper slag supported nanoscale zero-valent iron (nZVI/copper slag) adsorbent was used to effectively reduce the concentration of arsenite in water. Optimization experiments showed that the adsorbent could remove a significant amount of arsenite within a short period of time. The adsorption process followed the Langmuir model and pseudo-second order kinetics. By using pure copper slag as a substrate, the leaching of iron from the adsorbent surface was significantly reduced. Additionally, the magnetic properties and weight of the adsorbent allowed for easy separation from the aqueous media.