Removal of Cu 2+ ions with 2-phosphonobutane-1,2,4-tricarboxylic acid–modified nanoscale zero-valent iron

Abstract

Applications of nanoscale zero-valent iron (N-Fe⁰) and modified Fe⁰ with 2-phosphonobutane-1,2,4-tricarboxylic acid (P-Fe⁰) prepared by borohydride reduction for removal of Cu²⁺ in water are investigated under a variety of experimental conditions. Characterizations with X-ray diffractometer, scanning electron microscopy and transmission electron microscopy confirm that N-Fe⁰ and P-Fe⁰ have a core shell structure similarly. The uptake experiments investigated the effects of the dosages of N-Fe⁰ and P-Fe⁰, pH and the adsorption kinetics. The results showed that the ratio of removal efficiencies is more than 90% with the condition of initial concentrations of 10.0–70.0 mg/L, pH of 7 at 25 °C and the adsorbent of 0.4 g/L N-Fe⁰ and P-Fe⁰. Within the applied conditions, the order rate of Cu²⁺ adsorption kinetics equation on the N-Fe⁰ and P-Fe⁰ was the pseudo-second. According to X-ray photoelectron spectroscopy results, Cu²⁺ ions were removed primarily via a redox mechanism that resulted in the formation of Cu⁰ and Cu₂O. The contact of N-Fe⁰ and P-Fe⁰ with aqueous media caused extensive formation of iron oxide. The research reveals that Cu²⁺ can be efficiently removed by the means of N-Fe⁰ and P-Fe⁰ in solution, and the appropriate factors, involving pH value and the dosages of Fe⁰, were important keys in the process, and the modified Fe⁰ will be extensively utilized for the removal of Cu²⁺ from wastewater.