Optimization of Nickel Removal and Discovery of a New Method Leading to the Synthesis of Nickel Iron Carbonate Hydroxide Hydrate (Fe2Ni2(CO3)(OH)8,2H2O)

Abstract

Given its impact on human health and the environment, wastewater containing harmful metals such as nickel must be treated before being discharged. In this context, the current study focuses on the optimization of operating parameters influencing the elimination of nickel by electrocoagulation. Various operating conditions were studied, including electrical voltage, inter-electrode distance, agitator geometry, electrode surface, and electrolysis time. The obtained results are promising. The Al electrode demonstrated superior metal removal performance compared to the Fe electrode. The maximum Ni removal efficiency, after 20 min of electrocoagulation under an electrical voltage of 6 V, reached 90 %, using aluminum electrodes, with an immersed surface of 8.95 cm2, and anchor stirrer (24 rpm).The characterization of the precipitates formed during electrocoagulation provided valuable insights into the mechanisms underlying nickel removal. The first mechanism revealed that nickel ions were converted into nickel hydroxide, which then adsorbed onto aluminum hydroxide, resulting in the formation of easily decantable flocs. The second mechanism showed that the electrocoagulation of nickel ions with iron electrodes led to the formation of Nickel Iron Carbonate Hydroxide Hydrate, a compound that can serve as a corrosion inhibitor.