The Research On Antimony Removal In Raw Water With Coprecipitation-ultrafiltration

With the continuous development of Antimony-industry in China, the usage amount of antimony has been rising in our country at present; As the way of Antimony-industry development in our country is extensive and unsustainable, the problem of Antimony-industry pollution has become a hot issue in the field about heavy metal pollution. Antimony-pollution are mainly distributed in the air, soil and water; People access to the Sb in environment though potable water, breathing, food and other ways. Antimony is mainly harmful to our skin, internal organs, and respiratory tract etc. Considering that antimony is poisonous and carcinogenic to our human body to some extent, many countries have formulated the strict environmental standards for antimony content. Chinese regulations on hygienic standards for drinking water rule that the content of antimony shall not exceed5μg/L.The paper studys the process of trace antimony removal in rawwater with coprecipitation-ultrafiltration. First, contrast the effect of various coagulants in removal of antimony. Results show that the effect of iron-salts coagulant is better than aluminum-salt coagulants in antimony removal; Besides, the experiment also studied that the influence of various factors (such as mixing time, pH, temperature, etc.)on the coprecipitation-ultrafiltration removal of antimony; Then, treat the clear liquid by ultrafiltration after coprecipitation, the concentration of antimony in produced water can meet the standard requirements. Finally, the pollution-mechanism and cleaning-method of ultrafiltration membrane was analyzed.The main mechanism of the process using coprecipitation-ultrafiltration to remove antimony in this issue is as follows:the hydrolysis of coagulant precipitation product through the surface adsorption, parcel (left) and generate mixed crystal into solid solution and so on; antimony acid radical, antimony and other ions have an coprecipitation in the water, then the part of the amorphous precipitate, colloids, or macromolecular solute not been settling to remove were reteinde by ultrafiltration membrane sieving intercept. The issue also analysis the effect of the affecting factors in the antimony removal:(1) The dosage of coagulant, the influence of coprecipitation agent dosage to coprecipitation-ultrafiltration process in antimony removal:with the sucken cast coprecipitation agent dosage was larger, the increase of the amount of antimony removal rate increased gradually; when the dosage of ferric chloride additive in the raw water amount to10/L, antimony removal rate reached86.74%in raw water, precipitation supernatant after ultrafiltration membrane, the antimony removal rate reached96.96%, then increase the dosage of coprecipitation had no obvious improvement to antimony removal rate.(2)The length of stirring time, the influence of the stirring time length on antimony removal mainly depends on the time needed in the impurity ions adsorption when precipitation formed; If the stirring time is not enough, precipitation has not been formed, then the removal rate of antimony is affected. While mixing time is too long, it will arise precipitation aging phenomenon affecting the removal rate of antimony as well. The experiment ensured that the optimal mixing time is5-10min.(3) The pH valuo, pH of raw water of has a significant effect on antimony removal in coprecipitation of ultrafiltration technology, finally confirmed that the optimal pH range of antimony removal in the coprecipitation-ultrafiltration process is in neutral condition (pH6-8), antimony removal rate will be over95%in this range.(4) The temperature, the influence of the test temperature on antimony removal is small, when the temperature of30degrees or so,the removal effects to the best,while the room temperature is20degrees or so, the raw water of antimony removal rate can reach more than95%. Besides, the study found that under the condition of low temperature, the antimony removal effect is good, but membrane pollution is serious, so it is concluded that the water temperature is one of the important influencing factors in membrane fouling.Dynamic experiments show that under the condition of continuous water, adjust the raw water turbidity, measureing water turbidity and concentration of antimony can conform to the requirements of the drinking water, the effect of coprecipitation-ultrafiltration process in antimony removal is remarkable, this process has a good application prospect on the slightly polluted raw water governance.