| Antimony is a non-essential element of human being,its toxicity is similar to that of arsenic,and it has accumulated toxicity,teratogenicity,and carcinogenicity.The main existing treatment technology of antimony containing wastewater treatment is still coagulating sedimentation and adsorption based on ferric salt and aluminum salt.As a result of the“anion absorption edge”phenomenon,the antimony can be effectively removed under the condition of acid or weak acid,but the efficiency of antimony removal is sharply decreased under neutral or alkaline conditions.Hence,in order to control and reduce health risks and the impact of antimony in contaminated water bodies on environment,the research and development of safe,efficient,environmentally friendly,practical and effective removal of antimony and the application of novel flocculants-adsorbents for deep removal of antimony is currently an important direction in the field of wastewater treatment.In this dissertation,industrial poly-aluminum chloride and lime being raw materials,Ca-Al LDHs prepared with Ca/Al molar ratios of 2:1 and 3:1 using the“salt-?hydroxy?oxide method”at room temperature under strong stirring conditions,Ca-Al LDHs were characterized by XRD,FT-IR,TG-DSC,BET,SEM-EDS,and confirmed that the synthesized materials were Ca-Al-Cl LDHs.Ca-Al LDHs prepared with Ca/Al molar ratios of 2:1 have better removal performance with Sb?III?.In the initial solution pH range for 3.011.0 the removal rate stable between88.1890.68%;Ca-Al LDHs dosage is 0.4g·100mL-1 and shaking contact time 300min can achieve adsorption equilibrium.The removal Sb???process can be well fitted with the second-order kinetic model and linear correlation coefficient of 0.9999.At different temperatures,the Sb???removal process can be well fitted with the second-order kinetic model and linear correlation coefficient of 0.9999.Freundlich adsorption isotherms for the adsorption of Sb???linear correlation coefficient all greater than 0.9792,Separation factor RL is between 0.146 and0.873.Thermodynamic parameters?H0<0,?G0<0,?S0>0,shows that the removal process was a spontaneous,exothermic and entropy increase process.The solid-liquid interface is random for the adsorption of Antimony on Ca-Al LDHs.The removal of Sb?III?is dominated by uneven surface adsorption and edge adsorption.Ca-Al LDHs prepared with Ca/Al molar ratios of 3:1 have better removal performance with Sb???.In the initial solution pH range for 3.011.0,the remaining Sb?V?concentration between 1520?g·L-1,and removal rate stable between 97.9999.10%;In particular,the removal process no“anion absorption edge”phenomenon.Ca-Al LDHs dosage is 0.3g·100mL-1 and shaking contact time 120min can achieve adsorption equilibrium.The co-existing anions of Cl-,CO32-in solution inhibits the removal of Sb?V?,the presence of PO43-is more complex.The removal Sb???process can be well fitted with the second-order kinetic model and linear correlation coefficient of 1.000.Removal process of Sb???can be well fitted with the Freundlich adsorption isotherms,and the temperature increase is favorable to the removal of Sb?V?.The characterization of the precipitate before and after the removal of Sb?V?shows that Sb?OH?6-enters the interlayer to replace part of the Cl-and CO32-ions.The removal of Sb?V?is dominated by chemical adsorption and ion exchange.The synthesized Ca-Al LDHs can reduce the total antimony concentration in the pit wastewater from 1360?g·L-1 to 32?g·L-1.The combination of Ca-Al LDHs and PAFC flocculants reduces the total antimony concentration to 24.4?g·L-1,and the effluent pH is between 8.5 and 9.0,which is an order of magnitude lower than 0.3mg·L-1for the National emission standards of tin,antimony and mercury?GB30770-2014?.At the same time,meet the“Discharge standard of pollutants for municipal wastewater treatment plant”?opinion soliciting draft?in the total antimony emission concentration of less than 50?g·L-1 standard.This shows that Ca-Al LDHs can be used as a potential flocculating adsorbent for removing antimony from mine drainage. |
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