Three-dimensional Electrolysis-adsorption Combined Technology For Treatment Of Desulfurization Wastewater

The composition of the sintering flue gas desulfurization wastewater is complex.The Values of COD,ammonia nitrogen,suspended solids,heavy metal ions,chlorides,and fluorides are excessive and they are serious to the environment.The wastewater treated by conventional methods is difficult to meet desulfurization wastewater discharge standards,therefore,it is necessary to carry out treatment of desulfurization wastewater.The three-dimensional electrolysis method has the advantages of high wastewater treatment efficiency,simple equipment,convenient operation,no need to add any chemical agents,no secondary pollution,and so on,so it has obvious advantages in the application of wastewater treatment.Adsorption method has a good effect on the removal of pollutants from wastewater,because of the highly developed pore structure of adsorbents.In this study,the three-dimensional electrolysis-adsorption combined technology was used for the treatment of desulfurization wastewater.In the three-dimensional electrolysis experiment,5×10 cm titanium mesh and tantalum-coated titanium mesh were used as the anode and cathode of the main electrode plate,and activated carbon was used as the three-dimensional particle filler.The effects of factors such as particle size of the filler,initial pH of the wastewater,electrolysis voltage,electrolysis time,distance between the plates,dosage of particle filler on the COD and ammonia nitrogen removal of the desulfurization wastewater were examined and the best experimental parameter conditions were obtained.The results showed that for the removal of the COD and ammonia nitrogen,the optimum particle size was 4mm,the initial pH of the wastewater was 3,the electrolytic voltage was 20 V,the electrolysis time was 2h,the plate distance was 8cm,the particle filler dosage was 100g/L.Under the optimal conditions of three-dimensional electrolysis process,the COD and ammonia nitrogen removal rates were 79.2% and 99.7%,respectively.During the experiment,according to the BOX-Behnken principle,electrolysis time,electrolysis voltage,and particle filler dosage were used as test factors,and COD removal rate was used as a response surface to establish a response surface model,using Design Expert software.According to Box-Behnken test design and analysis of variance,the interaction between electrolysis time and electrolysisvoltage was significant.The optimized test results showed that the electrolysis time was 180 min,the electrolysis voltage was 21.5 V,and the particle packing dosage was86.5 g/L.Under those condition,the COD removal rate were 80.4%.Through the verification test,the relative errors were 2.4%,3.1%,and 1.1%,respectively,so the model had good simulation results.The stability of the particle packing was investigated and analysis by scanning electron microscopy(SEM).The results show that the particle electrode is still stable after using 25 times.In the adsorption test,the adsorption capacities toward COD of four adsorbents,SD300 macroporous resin,ZGA307 strongly basic anion exchange resin,D201 macroporous anion exchange resin,and coconut shell activated carbon,on the removal of COD from desulfurization wastewater were investigated,at the same time,The optimal adsorbent dosage,adsorption time,and pH of suitable wastewater for the coconut shell activated carbon adsorbent were investigated.The results showed that the optimum adsorption amount of coconut shell activated carbon was 30g/L,the best adsorption time was 30 min and the adsorption effect is not affected by the pH of the wastewater.The COD removal rate was 27.1%,and the COD concentration was 166mg/L after the electrolyzed desulphurization wastewaterwas treated by adsorption.The desorption of coconut shell activated carbon with 0.2 mol/L dilute hydrochloric acid was performed during the experiment,and the desorbed coconut shell activated carbon was analyzed by SEM and BET.The results showed that the desorption effect was good.Therefore,this experiment selected three-dimensional electrolytic-coconut shell activated carbon adsorption combined technology as an desulfurization wastewater treatment method.The results indicate that for the best electrolysis conditions of the combined process,the particle size is 4mm,initial pH is 3,electrolysis time is 128 min,electrolytic voltage is 21.5V,plate distance is 8cm,and the particle filler dosage is 86.5g/L;and for the best adsorption conditions of the combined process,the coconut shell activated carbon dosage is 30g/L,the adsorption time is 30 min.The desulphurization wastewater treated by the combined process can meet the the indirect discharge requirements of(GB 13456-2012)water pollutant discharge standard of iron and steel industry.