Study On The Efficiency Of Coagulation Sedimentation To Remove Sb(Ⅲ) And Sb(Ⅴ) From Water And The Influence Of Matrix

Antimony is a homologous element of arsenic with similar properties.It can enter the human body through the respiratory tract,digestive tract and skin,causing antimony poisoning.With the widespread application of antimony and its compounds in daily life,the pollution of antimony to the environment is becoming more and more serious.Antimony in the environment is eventually classified into natural water bodies through natural circulation,which destroys the ecological environment and brings hidden dangers to the health of residents.Many countries list antimony as a highly hazardous toxic pollutant.Many countries list antimony as a highly hazardous toxic pollutant.China’s antimony reserves and production rank first in the world.In recent years,antimony pollution incidents have occurred frequently.How to efficiently remove antimony in polluted water bodies has become one of the global environmental problems that need to be solved urgently.Many countries in the world had conducted a lot of related research on the removal of antimony,but the current antimony removal technology is not yet mature.The coagulation sedimentation method has good treatment effect and low operating cost,and is widely used in actual water treatment.This paper studies the removal efficiency of two new types of coagulants-zirconium tetrachloride and titanium tetrachloride on inorganic Sb（Ⅲ）,organic Sb（Ⅲ）and Sb（Ⅴ）under different solution conditions,and compares them with traditional coagulation.The antimony removal efficiency of aluminum trichloride and ferric chloride was compared and analyzed.The main research results obtained are as follows:（1）The removal efficiency of different coagulants on inorganic Sb（Ⅲ）,organic Sb（Ⅲ）and Sb（Ⅴ）was determined.When p H=4～10,four coagulants were used to remove three different forms of antimony.The study found that compared with alkaline conditions,each coagulant had better antimony removal effect under acidic conditions.Taking China’s drinking water antimony limit（5μg/L）as the standard,for the removal of Sb（Ⅲ）,no matter inorganic or organic form,zirconium tetrachloride,iron trichloride,and titanium tetrachloride are all under certain conditions.Sb（Ⅲ）of 200μg/L can be reduced to less than 5μg/L.The second-order reaction rate constants of zirconium tetrachloride,iron trichloride,and titanium tetrachloride to remove Sb（Ⅲ）are:0.004（μg/L）^-1min^-1,0.0036（μg/L）^-1min^-1,0.002（μg/L）^-1min^-1.For the removal of Sb（Ⅴ）,zirconium tetrachloride and titanium tetrachloride have better antimony removal effects,while the removal effects of iron trichloride and aluminum trichloride are not ideal.The second order reaction rate constants for removing Sb（Ⅴ）by zirconium tetrachloride,ferric chloride and titanium tetrachloride are:0.0003（μg/L）^-1min^-1,0.0001（μg/L）^-1min^-1,0.0533（μg/L）^-1min^-1.The Langmuir adsorption isotherm equation can better fit the coagulation removal process of Sb（Ⅲ）and Sb（Ⅴ）.By comparing the fitted Langmuir adsorption constants,it can be seen that the hydrolysate of zirconium tetrachloride has the best adsorption affinity for Sb（Ⅲ）Strong,titanium tetrachloride hydrolysate has the weakest adsorption affinity for Sb（Ⅲ）;ferric chloride hydrolysate has the strongest adsorption affinity for Sb（Ⅴ）,and titanium tetrachloride hydrolysate has the strongest adsorption affinity for Sb（Ⅴ）The weakest.（2）According to the removal effect of different coagulants on different forms of antimony,it is found that the difficulty of removal of different forms of antimony is different.Compared with Sb（Ⅴ）,Sb（Ⅲ）is easier to remove,and organic Sb（Ⅲ）is easier to remove than inorganic Sb（Ⅲ）.In addition to the electrical neutralization and adsorption between the organic Sb（Ⅲ）and the coagulant,there may be complexation,which increases the amount of antimony adsorption.When the p H is4～10,Sb（Ⅴ）mainly exists in the form of negatively charged ion Sb（OH）₆^-,which increases the negative charge in the coagulation system,decreases the Zeta potential,and causes the coagulant colloid.The electrostatic repulsion between particles is enhanced,and it is more difficult to aggregate and grow between particles.The number of adsorption and binding positions provided by the hydrolyzed precipitate of the coagulant to antimony is reduced,resulting in a decrease in the amount of antimony adsorption.（3）The influence of the main matrix in the water on the antimony removal efficiency of each coagulant was determined.The presence of phosphates,silicates,sulfates and humic acid has an inhibitory effect on the antimony removal efficiency of each coagulant.Comparing the removal process of Sb（Ⅲ）and Sb（Ⅴ）,it is found that the process of removing Sb（Ⅴ）by coagulation is greatly affected by the matrix.Among the four substrates,humic acid has the greatest influence on the efficiency of antimony removal by coagulation.The ways to influence the antimony removal process of coagulation are as follows:increase the negative charge of the coagulation system and compete with antimony for adsorption on the surface of metal precipitates.,The complex reaction with the surface of the precipitate changes its surface properties and interferes with the hydrolysis process of the coagulant.Under the influence of the matrix,the antimony removal ability of each coagulant shows different changes.When there is water matrix,zirconium tetrachloride has the best antimony removal effect compared to other coagulants,and the antimony removal process is least affected by the matrix.