Study On The Residual Organics Removal From Manganese Electrochemical Solution By Fenton Process

Manganese is an important metal that widely used in metallurgy and chemical industry. With the rapidly growth of demand, the reserve and grade of manganese carbonate ore was fallen sharply, so it is important to develop and utilize manganese oxide ore. In recent years, some works have demonstrated the potential use of carbohydrates, agriculture and forestry byproduct as reducing agent to leaching manganese oxide ore in diluted acid medium. And the reductants have the advantages of high efficiency, environmental protection and low price. However, it would produce a lot of organic derivatives such as small molecular organic acid and aldehydes during the leaching of manganese ores. The organic derivatives may cause a certain influence to the electrolysis efficiency and corrosion the anode plate. Hence, it is necessary to remove the residual organic from manganese electrochemical solution.The oxidation removal process for the residue organics using Fenton reagent as the oxidizing agent was statistically analyzed in manganese electrochemical solution. Chemical oxygen demand (COD) removal has been chosed as the target parameter to evaluate the removal rate. The main contents were as follows:Single-factor experiments were employed to examine the influences of initial pH, ferrous ions concentration, H2O2/Fe2+ratio, reaction time and reaction temperature on the effects of COD removal rate. The results showed that the initial pH concern the Fenton reaction on the rails, and higher or lower pH will inhibit the reaction. Fe2+is the catalyst of Fenton, it can effectively promote the formation of HO-to decomposition the residual organic, but higher concentration will cause the invalid decomposition of H2O2. Warming will lead to the invalid decomposition of H2O2. It could get the COD removal rate about 75.35% under the initial pH 3.50, ferrous ions concentration 0.03 mol-L’1, H2O2/Fe2+ratio 5, reaction temperature 30 ℃, and reaction time 60 min.The effect of important parameters, such as initial pH, ferrous ions’ concentrations and the ratios of [H2O2]/[Fe2+], were investigated and the process conditions were optimized by using response surface methodology (RSM) based on Box-Behnken design (BBD). The results show that the effect of ferrous ions’ concentrations on the COD removal rate is the most significant, the effect of H2O2/Fe2+ratio is second, and the effect of initial pH is minimum. The removal rate of COD reaches 74.50% under the conditions of ferrous ions concentration 29.47 mmol·L-1, H2O2/Fe2+ratio 5, the initial pH 3.11. The values were similar to the predicted ones that less than 2% error. It is proved feasible to use Fenton method removing the residue organics in manganese sulfate solution.The analysis of UV scanning shows that the organic compounds in the manganese electrolyte are mainly small molecules. Fenton reaction process is very rapid,a little amount of organic molecules in solution is not oxidized and decomposedwith extension of reaction time; The detection of Fenton reaction pH valueshows thatthe increase of temperature leads to the decrease of pH value of manganese electrolyte but the lower initial pH value leads to the decrease of Fenton reaction removal effect. The pH value of manganese electrolytic solution is significantly lower than that of manganese sulfate solution, which shows that a certain amount of acid is produced in the process of degradation of organic compounds in Fenton reaction.The effects of different concentrations of Mn2+ SO42-, F- and Cl- ions on the Fenton reaction were investigated, in which Mn2+ and Cl- ions inhibited the Fenton reaction and lead to the decrease of COD removal rate. SO42- ion had no effect on Fenton reaction. The inhibitory effect of Mn2+on Fenton reaction was hindered due to the reaction of F- ions with Mn2+ but an excess amount of F- ions leads to the decrease of COD removal rate.