| With the increasing demand for the rare and precious metals such as gold and silver,the mining and extraction scale of gold and silver in mines is expanded,and the discharge of cyanide containing wastewater in metallurgical industry,especially in gold mines,is increasing.The cyanide containing wastewater is toxic and widely distributed,which is easy to cause serious harm to human,animal and natural environment.Therefore,it must be treated strictly.Based on the advantages of ion-exchange fiber in wastewater treatment,combined with the previous research work,a new type of ion-exchange fiber was developed,and its application in the treatment of cyanide containing wastewater was discussed,which laid the foundation for the development of an economic,efficient and safe treatment technology of cyanide containing wastewater.In this paper,a cheap and available polypropylene(PP)fiber was used as the matrix,the divinylbenzene(DVB)and styrene(ST)were used as the crosslinking and grafting agents,a grafted matrix fiber was obtained by the chemical solution grafting reaction,then the acylation reaction was carried out with trichloroacetyl chloride as acylating agent,and the acylation strong alkaline ion exchange fiber(ASA-IEF)was obtained by amination reaction with trimethylamine as aminating agent.This method avoids the traditional complex radiation grafting process and carcinogenic chloromethylation reagent(chloromethyl ether),and the synthesis process is more environmentally friendly.By optimizing the reaction temperature,reaction time and the amount of acylation reagent,the optimal reaction conditions were determined as follows:reaction temperature 30℃,reaction time 4 h,the ratio of CCl3COCl/St is 1:1.2.Under this condition,asa-ief has a high exchange capacity of 2.53mmol/g.The fibers were characterized by FT-IR,SEM-EDS,TG-DTA and chemical titration.The results showed that the surface structure and morphology of the fibers changed greatly after the reaction,and the acylation and amination reactions were successful.At the same time,the fibers had good thermal stability,acid and alkali resistance and oxidation resistance.Based on the experiment of static adsorption,dynamic adsorption,desorption and regeneration,the adsorption properties of copper cyanide complex and zinc cyanide complex on ASA-IEF were studied.The results show that the adsorption rate of copper cyanide complex and zinc cyanide complex is more than 85%when the solution pH is 8-10,the adsorption temperature is room temperature,the total cyanide concentration is 600 mg/L,and the adsorption equilibrium time is 7 min;for the actual cyanide wastewater,when the ratio of wastewater treatment capacity to fiber mass is 100/3(ml/g),the adsorption rate of total cyanide is 92%,and the adsorption equilibrium time is 17min.The results show that hydrochloric acid has a good desorption performance for copper cyanide complex and zinc cyanide complex,the desorption rate is more than 80%,the desorption rate of sulfuric acid for Zn(CN)42-is more than 95%,but the desorption rate for Cu(CN)42-is less than 50%;asa-ief can still maintain a high adsorption capacity after nine successive adsorption/desorption cycles with hydrochloric acid as desorption solution.The results of adsorption thermodynamics and adsorption kinetics show that the adsorption kinetics of ASA-IEF is in accordance with the lagergren quasi second-order kinetics model,and the adsorption rate is faster,and Freundlich adsorption isotherm model can better describe the adsorption process of ASA-IEF for metal cyanide complex.FT-IR and potentiodynamic tests showed that the adsorption of Zn(CN)42-,Cu(CN)42-by ASA-IEF was mainly ion-exchange,and the adsorption mainly occurred on the fiber surface.EDS results show that there are a lot of Cu(CN)42-and Zn(CN)42-on the surface of ASA-IEF.After adsorption,the content of Cu on the surface is significantly higher than that of Zn.Therefore,the adsorption effect of fiber on Cu(CN)42-is better. |
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