| With the rapid development of non-ferrous metallurgical industry,the emission of wastewater containing arsenic is increasing,resulting in serious pollution of surface water and groundwater.With the increasingly stringent national legislation on arsenic wastewater,highly efficient arsenic removal from non-ferrous metal smelting wastewater is thus required.Herein,a new combined process for arsenic removal,i.e.,ferrous co-precipitation/nanocomposite resin adsorption,was proposed for arsenic removal from wastewater from a tungsten mine smelter in Jiangxi province.The process parameters were optimized,and its feasibility was also evaluated.As for co-precipitation,ferric chloride was added for removal of arsenic at high concentration.Meantime,calcium chloride was introduced to remove silicate in the wastewater and thereafter enhance arsenic removal.The removal rate of arsenic was higher than 93%under the optimal conditions,i.e.,ferric chloride,520 mg/L;calcium chloride,300 mg/L;pH,6.5;agitation rate,50 rpm;reaction time,60 min;precipitation time,20 min,and As(Ⅲ)species were completely removed.As for trace arsenic removal by nanocomposite resin adsorption,a newly developed nano-zirconia-loaded composite resin in our laboratory HZO-201 and a commercially available nano-iron-loaded composite resin HFO-201 were compared because of their excellent arsenic removal performance.Transmission Electron Microscope images showed that nanosized HZO and HFO was well dispersed in the pore of the composite materials respectively.The surface area of both nanocomposite resins was larger than the host resin D201.HZO-201 showed higher arsenic removal capacity than HFO-201.Effluent after coprecipitation was collected as the feeding solution for column adsorption by HZO-201.After adsorption,arsenic in the effluent was below 0.5 mg/L,the maximum level required by national wastewater discharge standards(GB8978-1996).The treatable volume per run was-220BV at the flow velocity of 5 BV/h and the ambient temperature of 25℃.The exhausted HZO-201 could be effectively regenerated by a binary solution of 5%NaOH+5%NaCl,and the desorption rate above 98%.Further,the feasibility of the proposed process was considered,including the economic analysis,security analysis of precipitates and the harmless treatment of desorption solution from regeneration of the nanocomposite resin.The results indicated that the arsenic-laden precipitate met the entering standard of hazardous waste landfill.To sum up,zero arsenic emission from such alkaline wastewater could be achieved based on the new process. |
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