Experimental Study On The Treatment Of Alkaline Mine Flotation Wastewater Based On O₃/AC Coupling Process

Mine flotation wastewater has become one of the key industrial pollution to be solved in China,and the residual flotation chemicals in it are the main factors leading to the exceedance of COD,p H and other indexes of mine flotation wastewater,and it is important to find the process method for efficient treatment of mine wastewater containing flotation chemicals to promote the construction of green mining development.Based on this,two typical flotation chemicals,diethyldithiocarbamate and butyl xanthate,were selected in this paper,and the O₃oxidation,AC adsorption and O₃/AC coupling process were used to treat the simulated wastewater containing diethyldithiocarbamate,butyl xanthate and the actual alkaline mine flotation wastewater respectively.The main results showed that:（1）Ozone（O₃） and activated carbon（AC）alone have certain removal potential for diethyldithiocarbamate and COD,butyl xanthate and COD,but neither can achieve efficient simultaneous removal of diethyldithiocarbamate/butyl xanthate and the corresponding COD at the same time.The O₃/AC coupling process was formed by coupling the two,（1）at the initial mass concentration of diethyldithiocarbamate of 400mg/L,initial p H of 7.8,O₃and AC dosage of 3.00 g/h and 1.50 g/L,respectively,and50 min of reaction,the removal rates of diethyldithiocarbamate and COD could reach99.8%and 80.7%,respectively,which were 29.7%and 9.9%higher than those of activated carbon treatment alone;（2）At the initial concentration of 400 mg/L of butyl xanthate,initial p H of 7.5,O₃and AC dosage of 1.5 g/h and 1.50 g/L,respectively,and 60 min of reaction,the removal rates of butyl xanthate and COD by O₃/AC coupling process could reach 99.9%and 77.2%,and the COD removal rate was34.3%higher than that of O₃treatment alone,and the removal rates of butyl xanthate and COD were 31.8%and 8.1%higher than that of AC treatment alone.（3）The reaction time for the O₃/AC coupled process to achieve the maximum removal effect in the removal of diethyldithiocarbamate and its COD,butyl xanthate and COD could be reduced from 80 min to 50-60 min for the AC treatment alone.（2）The results of reaction kinetic analysis showed that the reaction processes of O₃,AC and O₃/AC processes for the removal of diethyldithiocarbamate and COD,butyl xanthate and COD were in accordance with the proposed primary reaction kinetic model.For the removal of diethyldithiocarbamate and COD,the apparent rate constants were k_（O3/AC）>k _O3>k _ACand k_（O3/AC）>k _AC>k _O3,respectively;for the removal of butyl xanthate and COD,they also showed the same phenomenon,and the apparent rate constants were k_（O3/AC）>k _O3>k _ACand k_（O3/AC）>k _AC>k _O3,respectively.It was inferred that the apparent reaction rate constants of the O₃/AC coupled process for the removal of diethyldithiocarbamate and COD,butyl xanthate and COD were greater than those of the O₃and AC treatment processes alone.（3）UV-vis spectroscopy and GC-MS analysis were used to speculate the degradation pathways of diethyldithiocarbamate and butyl xanthate,and the results showed that:（1）the removal of diethyldithiocarbamate and butyl xanthate by activated carbon（AC）was purely physical adsorption,and no other intermediate substances were generated;（2）diethyldithiocarbamate may have generated CS₂and S-C-S groups and other intermediate organic products that contribute to COD value under the action of O₃,O₃/AC,and GC-MS identification analysis showed that N,N-diethylformamide(C₅H₁₁NO)was generated under the action of O3,and further degraded to N-formyl-N-methylformamide（C₃H₅NO₂）under the action of O₃/AC;（3）For butyl xanthate,other intermediate organic products such as peroxynivalenol may have been generated under the action of O₃and O₃/AC that contributed to the COD value,and the GC-MS identification analysis showed that the intermediate organic products were butyric acid and other substances.（4）Based on the experimental parameters accumulated from the previous simulated wastewater treatment experiments with diethyldithiocarbamate and butyl xanthate,the COD removal rate of the actual mine flotation wastewater（COD of502.0 mg/L）treated by the coupled O₃/AC process after 3 times dilution was 93.3%after 210 min of reaction,which was 65.1%higher than that of the undiluted treatment,and 31.1%higher than that of the O₃and AC processes alone.The COD removal rate was 93.3%after 210 min of reaction,which was 65.1%higher than that without dilution treatment,and 31.5%and 83.3%higher than that of O₃and AC treatment respectively.Meanwhile,according to the p H monitoring results,the dilution pretreatment is beneficial to the O₃/AC coupling process to improve the p H of the actual molybdenum separation wastewater,and at a dilution of 3 times,the p H of the reaction 210 min can be rapidly reduced from 12.1 to about 4.5,which is lower than the GB25467-2010 emission standard,but the p H of the reaction 196 min is reduced to about 6.0,and the COD removal effect can be combined with the COD removal effect.It can be deduced that the COD removal rate is about 88.4%and the corresponding COD concentration is about 58.1 mg/L,which can meet the requirements of GB25467-2010 emission standard:COD≤60 mg/L and p H 6～9 at the same time.