Adsorption performance of tetratitanate nanowhiskers for Ni2+ from aqueous solution and removal of Ni2+ from actual electroplating wastewater via successive oxidation and adsorption processes

Abstract

Layer-structured tetratitanate (Na0.98H1.02Ti4O9·3.3H2O) nanowhiskers with the mean diameter and length of 448 nm and 8.38 μm were hydrothermally synthesized at 180 °C using commercially available low-cost metatitanic acid (H2TiO3·nH2O) and sodium hydroxide as raw materials. With the use of the Langmuir adsorption model, the maximum adsorption capacities of tetratitanate nanowhiskers for Ni2+ from aqueous solutions at pH of 7 and 20–50 °C were as high as 146.4–175.4 mg/g. When Ni2+ complexes present in an actual electroplating wastewater (Ni2+, 0.28 mg/L; COD, 280 mg/L) were pre-oxidized by calcium hypochlorite (ClO−, 0.3496 mol/L), after the adsorption with the use of tetratitanate nanowhiskers (133.3 mg/L), the residual Ni2+ concentration was decreased to 0.045 mg/L. The residual Ni2+ concentration in the treated actual electroplating wastewater satisfies the thresholds for discharging municipal and electroplating wastewaters authorized by the Ministry of Ecology and Environment of China. The successive oxidation and adsorption method is practical in the treatment of actual electroplating wastewater containing stubborn Ni2+ complexes.