Catalytic oxidation of phenol waste waters by hydrogen peroxide with the help of step-type regulation by redox-potential

The change in redox-potential (Eh) and active reaction (pH) was studied under the catalytic oxidation of phenols by hydrogen peroxide in waste waters from the production of canning tin. In the capacity of a catalyzer were used tin ions present in waste water. After adding hydrogen peroxide Eh of waste water increased to +(550-580) mV. During the process of phenols oxidation Eh decreased to the value +(300-500) mV, and pH decreased from 6,2-6,3 to 1,1-1,6. This resulted in phenol oxidation to the required value of 0,2 mg/l. In decreasing Eh to +(130-150) mV the residual concentration of phenols constitutes only 1,25-1,90 mg/l. In the process of reaction the temperature of waste water increased to (44-48)0C. The increase of the starting dosage of hydrogen peroxide led to the decrease of pH below 1,1-1,0 and to the increased temperature of waste water to (60-70)0C and higher. Because of this the decomposition takes place of hydrogen peroxide with the emission of oxygen in the form of "vigorous boiling" of waste water in the mixer-reactor and the hindering of the process of phenol oxidation. For keeping optimum parameters of oxidation under conditions of changing the concentration of admixtures the step-type increase of redox-potential by hydrogen peroxide up to +(550-600) mV is proposed with supporting the value of pH by alkali in optimal limits from 5,5-6,0 to 2,4-2,6. The process of dosing reagents is implemented in a non-flowing mechanical mixer-reactor. The algorithm is presented of four-step dosing reagents in industrial conditions which is carried out in automatic regime. The automated step-type regulation of Eh and pH is perspective for treating waste waters from toxic admixtures with oxidation-reduction properties