Technical Study Of High-salinity Cyanide-containing Waste Water Using Heterogeneous Ozone-photocatalytic Oxidation Process

Cyanide,ammonia nitrogen-containing wastewater are widely exists in the manufacturing industry,mining industry and daily life.It will be very dangerous to the environmental security and the biological environmental condition if the cyanide,ammonia nitrogen-containing wastewater was discharged into the natural water.The conception of this research is regional economy coupling of cyanuric chloride,wastewater treatment,and Chlor-Alkali chemical,which is proposed under the concept of there isn't garbage can't be used,there is only resouce placed in the wrong location.In this paper,the research model is the cyanuric chloride process wastewater produced by sodium cyanidechlorine gas method.The energy reduction and waste water zero discharge is realized by employing the cyanide,ammonia nitrogen-containing wastewater with high salinity in the chlor-alkali chemical after treatment.and the product of chlor-alkali chemical can serve as the cyanuric chloride raw material.The in situ treatment of waste was deeply discussed experimentally under the conception of stepwise processing of the cyanide and ammonia nitrogen in this paper.The comprehensive treatment methods are heterogeneous ozone oxidation of cyanide,heterogeneous photocatalysis degradation of ammonia nitrogen and the nitrate nitrogen produced in the system.The reactor design,process design,operation parameter optimization,waste water treatment effect and the reaction model are investigated.And the main research results are as follows:The heterogeneous ozone oxidation of the CN^-and NH₄⁺ in the waste water was conducted in the three phase flow reactor designed in this paper.The effect of the activated carbon particle size,the activated carbon concentration,the ozone concentration,and pH on the degradation of the CN^-?NH₄⁺ was researched.The research result showed that the obvious synergistic effect was existed between the activated carbon and the ozone.And the cooperation factor was 1.36,cyanide removal rate reached 99.8% and the residual cyanogen content in the processed water was 0.3mg/L under the condition of activated carbon amount 10g/L,pH10,mixed gas flow of ozone/oxygen 3.2L/min,total ozone 30mg/min,ozone concentration 9.4mg/L,and 30?.The treatment effect of the heterogeneous photocatalytic oxidation-reduction system on the waste water was researched.The continuous three-phase fluidized photocatalytic reactor was developed to improve the effect of the reduction reaction.The granular supported AC/TiO₂ catalyst with activated carbon as a carrier was prepared.The research result showed that the nitrogen removal ratio was 98.02%,and the residual nitrogen content was 0.7mg/L under the condition of pH 11,UV light power 12 W,superficial velocity 40 m L/s,reaction temperature 60?,residence time 120 min,which was superior to the upper limit of chlor-alkali chemical industry of 4mg/L.In order to improve the photocatalytic velocity and the interconnected coupling of the heterogeneous ozone oxidation with photocatalytic process,the synergistic effect between the photocatalytic and the ozone was studied experimentally in the three phase flow reactor.The research result showed that the cooperation factor was 1.58,and the nitrogen removal efficiency exceeded 90%,the residual nitrogen content was 2.6³.3mg/L under the condition of pH 11,UV light power 12 W,AC/TiO₂ catalyst loading 10g/L?w?Ti O₂?=1.92%?,ozone flow rate 20 mg/min,residence time 50 min.The reaction mechanism of heterogeneous ozone-photocatalysis process was researched.It was confirmed that the function of activated carbon was concentrating the substrate in the system,which could provide the reaction surface for the reaction mass.And the photocatalytic ozone oxidation process was the combined action resulting from ozone adsorption on the AC/TiO₂,ozone direct oxidation and UV photocatalytic oxidating ozone to produce ·OH free radical,AC/TiO₂ motivating ·OH free radical indirect oxidation,the conduction band electrons of the AC/TiO₂ reducing peroxidation product.