Study On RDX-containing Wastewater Treatment By Homogeneous Catalytic Ozonation In Rotating Packed Bed

RDX-containing wastewater is produced during the production and use of RDX, whichwill cause serious harm to human health and ecological environment because of its complexcomposition, high toxicity and low biodegradability. RDX-containing wastewater treatmentmethods are generally divided into three categories which are physical method, advancedoxidation method and biological method. The energy consumption and cost of the physicaland biological methods are low, but when used alone, the physical method has disadvantagesof treating not thoroughly, recontamination and low removal rate etc., and the biologicalmethod has disadvantages of long degradation time and low degradation efficiency etc..Chemical method is relatively efficient and completely, but it just greatly improve thebiodegradability of wastewater, which is difficult to directly meet the national emissionstandards. Therefore, the research of a new, efficient and economic method of treatingRDX-containing wastewater becomes a current study hotspot.For the lack of an efficient method of treating RDX-containing wastewater, treatment ofit by homogeneous catalytic ozonation in rotating packed bed （RPB） was studied in thispaper.In the experiment,700mL RDX-containing wastewater （RDX concentration of50mg/Land COD=93mg/L） was treated using RPB-O₃, RPB-O₃/H₂O₂and RPB-O₃/Fentonrespectively. The results show that the latter two treatment methods are feasible.（1） Undernormal temperature,the optimum operation parameters of RPB-O₃/H₂O₂are high gravityfactor of75, initial pH=9,ozone concentration of42.7mg/L,H₂O₂:O3=0.3（mol:mol）,gas flowof75L/h and liquid flow of140L/h.After the wastewater is treated30minutes under theoptimum operation conditions, the removal rate of RDX reaches92.1%,and the RDX concentration and COD are3.95mg/L and48mg/L respectively.The effluent complies to thenational secondary emission standard.（2） Under normal temperature,not changing the originalpH value,the optimum operation parameters of RPB-O₃/Fenton are high gravity factor of85,Fe²⁺total dosage of2mmol/L（three times dosing）, H₂O₂:Fe²⁺=4（mol:mol）,ozoneconcentration of42.7mg/L,gas flow of75L/h and liquid flow of140L/h.After the wastewateris treated20minutes under the optimum operation conditions, the removal rate of RDXreaches97.5%,and the RDX concentration and COD of the effluent are1.25mg/L and35mg/Lrespectively. The effluent complies to the national primary emission standard.The treatment effect and ozone utilization rate of RPB-O₃/H₂O₂and RPB-O₃/Fentonwere compared with RPB-O₃.It is found that the addition of homogeneous catalyst, H₂O₂andFenton reagent,not only greatly improves the oxidation efficiency, but also improves theutilization rate of ozone by17.6%and27.9%respectively. Then the ozone utilization rate ofRPB and conventional aeration device are compared, finding that RPB can improve theozone utilization rate of O₃/H₂O₂and O₃/Fenton processes by64.5%and59.5%respectively.As to the problem that the total not used ozone in the exhaust was up to about40%in the12min reaction time for the above two homogeneous catalytic ozonation methods, twomeasures to further improve ozone utilization were done:（1） Reuse the exhaust ozone;（2）Change the reservoir size in order to increase gas-liquid contacting time.The experimentalresults show that the measures are effective. The ozone utilization rate of RPB-O₃/H₂O₂andRPB-O₃/Fenton with new process are increased by11.2%and8.4%respectively comparedwith the original process.In view of oxidation efficiency and ozone utilization rate, the relationship of the threetreatment methods is RPB-O₃/Fenton>RPB-O₃/H₂O₂>RPB-O₃. Compared with the other twomethods, RPB-O₃/Fenton can achieve the best treatment effect in the shortest time, andgreatly saves power consumption and ozone dosage, reducing treatment cost. So it is a new，efficient and energy saving method to treat RDX wastewater.