Abstract
Galvanic production in terms of the degree of negative impact on the environment occupies a leading position in the global industrial production; therefore, the introduction of regenerative recycling technology is receiving increasing attention. The aim of the present work is to determine the kinetic characteristics of the precipitation reaction in a solution of nickel sulfate with sodium hydroxide to develop a technology for the regeneration utilization of spent solutions of chemical nickel plating (SCNPS). The object of the study was the spent solution of chemical nickel plating of one of the industrial enterprises of Izhevsk. The experiment was carried out in the temperature range 293–333 K at various concentrations of sodium hydroxide (1.25–2.60 M) and nickel sulfate (0.037–0.06 M). To determine the order of the reaction, we plot graphs in the coordinates lg w – lg C(Ni) using the experimental data, where w is the reaction rate. The tangent of the slope of the obtained linear dependences with a high degree of approximation (R2 = 0.98) is close to 2, therefore, the order of the reaction of the deposition of SCNPS with sodium hydroxide is second. With a graphical method for determining the rate constant of a second-order reaction for the dependence 1/С = f(t), the tangent of the slope of the straight line corresponds to the calculated parameter. In the investigated temperature range the rate constant takes values from 5·10-4 to 9·10-4 dm3·mol-1·s-1. The activation energy of the precipitation reaction, determined by the Arrhenius equation by graphic and calculation methods, is 16.57 kJ·mol-1 and 16.44 kJ·mol-1, respectively. The low values of Ea indicate a weak dependence of the reaction rate on temperature. Consequently, the introduction of the technology for the regeneration utilization of SCNPS will not entail large expenditures of energy resources for heating the reaction masses.