| The studies on the electroplating chromium-containing waste-water treatment by using the iron-chipping internal electrolytic process and the production-oriented experiment of the iron-chipping internal electrolytic process have been presented in this paper. The main results of the study are as follows:1. Using the electroplating waste-water (Cr6+) of an electroplating workshop in Chongqing as an object of study, the removal rate of hexavalent chrome has been investigated through the single factor experiment and the orthogonal experiment under various conditions by using the iron-chipping internal electrolytic process. The single factor experiment showed that the longer the retention time was, the better the effect. However, after fast reacting at the begging, there was little change in the removal rate of Cr6+ with the time increasing. So, it would better to control the reaction time within about 50 min. The lower the pH value was, the better the effect. But if the influent had lower pH value, the iron consumption was more, the iron-chipping containing resolved in the water was increased and the chromaticity of the effluent was somewhat heavier. If the raw water was needed to add the acid to adjust the acidity, the addition amount of the acid for the operation with lower requirements was increased, as a result, the operating cost was increased. So, it would better to adjust the pH value to 3-4. The higher or lower volume ratio of Fe/C may have an influence on the removal rate of Cr6+. If this ratio was close to 1, the treatment effect was better. So, the volume ratio of Fe/C would be chosen to 1:1.5-1:1. The iron-chipping grain size was smaller, the treatment effect was better. But if the iron-chipping grain size was too small, it was easily lost in the practical engineering application and the thinner iron-chipping grain size may cause the plugging and agglomeration during the treatment. So, it would better to choose the iron-chipping grain size to 1-2mm. Based on the single factor experiment, the orthogonal experiment was carried out. The residence time, pH value, the volume ratio of Fe/C and the iron-chipping grain size were chosen as the study factors. The Cr6+ were used as the specification parameter to evaluate the treatment effect. The experiment results showed that the major and minor factors which influenced the treatment effect were pH value, the iron-chipping grain size, the volume ratio of Fe/C and the residence time in sequence. The optimum technological conditions were that pH value was 3.5, the iron grain size was 2mm, and the volume ratio of Fe/C was 1.5:1and the residence time was 50min. The experiment was optimized according to these technological conditions. The stable treatment effects and good reproducibility have been obtained. The removal rate of Cr6+ was up to over 99.1%.2. The production-oriented experiment study of the iron-chipping internal electrolytic process was carried out at a waste-water workshop in Chongqing. The former electrolytic cleaning treatment method was replaced by the iron-chipping internal electrolytic process to treat the electroplating chromium-containing waste-water. The production-oriented experiment was carried out on the existing treatment process. The experiment results showed that the removal rates of Cr6+, Ni2+, PO42- (with P) and CODcr have been up to 99.6%, 96.4%, 99.3% and 45.6% respectively, which were prior to the national class A discharge standard regulated by《The Waste-water Comprehensive Discharge Standard》(GB8978-1996). The treatment process of the iron-chipping internal electrolysis + the inclined tube settling basin + the oblique hole filter was a reasonable treatment process for treating the electroplating chromium-containing waste-water. It was characterized by the high treatment efficiency and stable operation. |
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