Nickel chloride removal and insights into heavy metal removal by hydrate-based method

Abstract

Heavy metal ion in waste water can be potential treated by hydrate formation and dissociation. In this work, nickel chloride was chosen for preparing heavy metal solution, which was then removed by forming methane (CH4) hydrate. Four common factors of stirring speed, hydration time, temperature, and concentration were considered respectively. The nickel chloride removal efficiency reached 71.8% with the dissociated water of 44.9% for the stirring speed, hydration time, temperature, and nickel chloride concentration of 400 r/min, 1 h, 271.1 K, and 100 ppm, respectively. Adhered heavy metal solution on the hydrate surface resulted in the impurity of heavy metal removal by hydrate-based method, and wrapped heavy metal solution by accumulated hydrate was another main reason for the impurity of heavy metal removal. In addition, a flushing water method was proposed and conducted. Nickel chloride removal efficiency was improved to 89.5% with the yield of dissociated water of 44.2%. Finally, controlling hydrate formation conditions and combining hydrate-based method with other method were also proposed to enhance the heavy metal removal efficiency.