Electrocoagulation In Wastewater Treatment at Mines and Quarries. Part 1. Pre-treatment Stage to Reverse Osmosis Units

In the present work, removal of hardness and strontium from synthetic wastewater by electro coagulation has been studied. Aluminum and steel electrodes have been used and removal efficiencies have been compared with respect to electro coagulation time, current density, pH, temperature and the chemical composition of solutions. The area of the working surface of the cathode is Sc = 176,6 cm², the aluminum anode is Sai = 42,4 сш², the steel anode is SFe = 49,5 от². The distance between the electrodes is 2.9 cm. Electrolysis of the solution (V = 0.4 L) is accompanied by an increase in pH and temperature. As a result of electrochemical dissolution of the anode material and hydrolysis of Al³⁺ (Fe³⁺) ions, an amorphous precipitate of the coagulant metal hydroxide is formed in the solution, nitrates are reduced on the cathode and hydrogen is released. After 1015 minutes (pH > 9, t > 30 °C), a characteristic smell of ammonia appears. The constants of the rate of decrease in the rigidity of the Кдж, calculated on the basis of the experimental data, vary within the range of 0.009-0.131 min^-1, depending on the anode material, the current density and the composition of the solution. In the electrolysis with the Fe-anode, the value Кдж = 0.051 min^-1 (J = 28 mA/cm²), which is twice as high as in the electrolysis with Al-anode under the same conditions. The electrolysis solution, in which before the experiment was diluted NaHCO3, with an Al anode at J = 24 mA/cm² for 30 minutes resulted in a nearly complete precipitation of Ca²⁺ and Sr²⁺ as carbonates by adsorption to aluminum hydroxides.

очистка воды, электролиз с растворимым анодом, электрокоагуляция

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