Microwave-activated Carbon Enhanced Treatment Of Shellac Wastewater And Activated Carbon Regeneration

Shellac is the only natural animal resin with excellent physical and chemical properties.It has a long history and a wide range of uses in China.However,the production process of shellac is accompanied by the problems such as scattered production areas,large sewage production,and difficult to treatment.At present,shellac wastewater treatment methods are mainly chemical oxidation methods,and supplemented by physical pretreatment methods,which have problems such as corrosion equipment,high energy consumption,and low efficiency.Microwave is a kind of chemical process intensification technology,which has the characteristics of fast heating speed and uniform heating,combined with the advantages of cheap and easy access to activated carbon,green environmental protection,easy regeneration,etc.,and the combination of the two has a synergistic effect and is suitable for the treatment of shellac wastewater.In this paper,microwave-activated carbon intensification technology is used to treat shellac wastewater.Microwave method is used to intensification regenerate activated carbon that has adsorbed shellac wastewater to realize the reuse of activated carbon to save resources and avoid secondary pollution.The main research contents are as follows:1.In this paper,the influencing factors and effects of microwave-activated carbon intensification technology treatment of shellac wastewater were discussed.Chemical oxygen demand（COD）,total nitrogen（TN）,total phosphorus（TP）,and five-day biochemical oxygen demand（BOD₅）were used as indicators.Through single-factor investigation and orthogonal experiment,the optimal treatment conditions were obtained:200m L of shellac wastewater,4.00g of powdered activated carbon,microwave power is 480W,radiation time is 6min,and the wastewater p H is 6-7.Under these conditions,the COD removal rate of the shellac wastewater were 85%,the TN and TP removal rates reach more than 90%,and the BOD₅ removal rate were 46%.2.Three contrast experiments were designed:microwave irradiation,activated carbon adsorption,and electric heating and activated carbon experiments.Under similar conditions,the highest COD removal rates of shellac wastewater were 8.5%,35%,and65%.the highest TN and TP removal rates were only 75%.Comparative experiments have proved that microwave-activated carbon intensification technology has a synergistic effect and can greatly improve the shellac wastewater s removal rates like COD,TN,TP and BOD₅.3.The Langmuir and Freundlich isothermal adsorption lines were used to simulate the pure activated carbon adsorption and microwave-activated carbon adsorption processes.It can be seen that the two adsorption processes are more consistent with the Langmuir adsorption model.The kinetic analysis experiments were performed on three different adsorbents:original activated carbon,regenerated one time activated carbon,and regenerated three times activated carbon.It was concluded that the adsorption of shellac wastewater by activated carbon was not suitable for the pseudo-first-order kinetic model description and intra-particle diffusion model,but was suitable for pseudo-secondary.It shows that the adsorption process is dominated by chemical adsorption.4.The used activated carbon was regenerated by the microwave intensification method.The six single factors of activated carbon quality,microwave power,microwave time,activated carbon p H,gas flow,and number of regenerations were investigated,and orthogonal experiments were designed.The best regeneration conditions are:4.00g of activated carbon mass,480W of microwave power,5min regeneration time,p H of activated carbon 7,nitrogen flow rate of 0.026 m³/h,and activated carbon can be reused more than seven times.The performance of activated carbon regenerated three times is the best.At this time,the loss rate of activated carbon is 7%,the COD removal rate of shellac wastewater is 93%,and the adsorption value of phenol can reach 204mg/g,which is 10%higher than the original activated carbon.FTIR,SEM,BET,etc.were used to characterize the activated carbon.The treatment costs of microwave-activated carbon intensification technology for the treatment of shellac wastewater and microwave intensification regeneration of activated carbon were discussed,and it was concluded that the cost of treating one ton of shellac wastewater was 187.75 yuan.