| The waste salt is the byproduct originated from the production of taimiocin,exhibited the characteristics of high content of sodium p-toluene sulfonate,complex organic composition and high basicity,which posed the potential of resource utilization.According to the composition characteristics of waste tymiomycin salt,the heat treatment characteristics of waste salt by one-step and two-step carbonization and the utilization of generated carbon were studied.The main research contents are as follows:(1)The main inorganic components in waste salt were Na2SO4 and NaCl,accounting for 26.34%and 6.61%,respectively.The main organic components were organic salt sodium p-toluene sulfonate,followed by impurities A,amphotericin,tern-butyl amine,p-toluene sulfonyl chloride and other by-products and incomplete reactants.The content of organic component was 29.50%(wt),as expressed by dissolved organic carbon(DOC).(2)The TG analysis of waste salt shows that the combustion and pyrolysis of waste salt can be divided into three stages,stage Ⅰ,stage Ⅱ and stage Ⅲ are room temperature～250℃,250～600℃ and 600～800℃ respectively.The combustion and pyrolysis of waste exhibited similar tendency in stage Ⅰ,while significant differences were observed for stage Ⅱ and Ⅲ.Specifically,the maximum weight loss stage occurred in stage Ⅱ for the two methods,and the weight loss rate of waste salt for combustion and pyrolysis are 49.30%and 71.57%,respectively.Simulated heat treatment in tubular furnace showed that the optimal heat treatment condition of waste salt is 500℃ for 2 h.The main components of tar produced in waste salt pyrolysis process are aromatic compounds with 2-4 rings,such as naphthalene,biphenyl and their derivatives,phenols,straight alkanes,oxygen-containing compounds,a few sulfur-containing compounds and nitrogen-containing compounds.The main components of the gas are H2,CO,CO2,CH4,H2S,SO2 and C2-C7 short-chain alkane.The solid product is carbon residue containingNa2SO4 and NaCl,and the DOC content of solid product is 17.68 mg/g.(3)The activated carbons prepared by one-step carbonization method at 600℃,700℃,800℃ and 900℃ were named as Z6,Z7,Z8 and Z9,respectively.The activated carbon named J57,J58 and J59 was prepared by the two-step carbonization method(the carbon precursor was obtained from a 2 h pyrolysis carbonization at 500℃,and then the carbon precursor was further carbonized for 2 h at 700℃,800℃and 900℃).The optimum preparation conditions for both methods were 800℃,2 h.The productivity of activated carbon is decreased with the increase of carbonization temperature,the yield of the preparation of activated carbon from one-step carbonization is a little higher than that of two two-step carbonization method.The organic carbon content of optimal carbon J58 from two-step carbonization method is 7.87%higher than that of optimal carbon Z8 from one-step carbonization method.The adsorption capacity of MB on activated carbon generated from two-step method was better than that of one-step method.The MB adsorption capacity of Z8 and J58 obtained by two methods was as high as 455.43 mg/g and 602.21 mg/g,respectively.The MB adsorption equilibrium time of activated carbon was 8 h,and the adsorption isotherms was followed by Freundlich model,indicating that the adsorption process of MB on activated carbon may be heterogeneous multi-molecular layer adsorption.The iodine adsorption capacity is higher than that of MB on activated carbon,and the iodine adsorption capacity of J58 is as high as 1.6×<103 mg/g.Activated carbon is a mesoporous material with rich micropores,abundant pore structure and large specific surface area,among which the total specific surface area of J58 is as high as 2.27×103 m2/g.There were no functional groups on the surface of activated carbon except C=S and-COO-.The adsorption of experimental activated carbon mainly depends on physical action,chemical action is weak.The gas products from the preparation of J58 is similar to the heat treatment characteristics of the research chapter,the liquid product is mainly composed of sulfur compounds,few heterocyclic aromatic compounds,in addition to the conventional oxygen compounds and nitrogen compounds and a small amount of phosphorus-containing compounds tar;The solid product is composed by carbon residue containing Na2SO4 and NaCl,and the DOC content is 5.40 mg/g.Activated carbon could be prepared by carbonizing the waste salt without additional activator,which is attributed the characteristic of high sodium p-toluene sulfonate content and high basicity in waste salt.This paper puts forward a method of recycling carbon from waste salt,which provides some reference for recycling other waste salt with high content of organic impurities or similar properties. |
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