Preparation Of The Materials For Heavy Metal Adsorption And Removal By Mechanochemistry

Coal-fired power plants are the main artificia l source in the atmospheric environment.The release of arsenic from coal w ill not only cause environmenta l pollut ion,but also reduce the activit y and treatment effects of the flue gas pollut ion control unit-SC R system,and increase the operation costs.Arsenic mainly exists as the form of oxide vapor（As₂O₃（g））during combustion process,which has high toxicity and strong migration property.Gaseous arsenic compounds can be concentrated on the surface of particulate matter through physical and chemical adsorption during combust ion process,and migrate and transform during the flue gas emission process.Alt hough more than 90%of gase ous arsenic can be removed by electric dust removal equipment after combustion,the consumption amount of coal is huge,a part of gaseous arsenic can still escapes into the atmosphere.Therefore,it is urgent to develop arsenic control methods which suitab le for high-temperature environments.In this study,attapulgite was selected as the carrier,and the composite adsorption material modified by manganese nitrate was prepared by mechanochemical method.The adsorbents were analyzed by XRD,TEM,BET,etc.,The effects of ball milling t ime,solid-to-liquid ratio,manganese loading,and ball-to-materia l ratio on the removal of gaseous arsenic were systematically studied.After optimizat ion,the sample was in full contact with the stainless steel ball,and the object was crushed,sheared,squeezed and other mechanical forces when the ball-to-materia l ratio was 1:10 and the solid-liquid ratio was 1:1,showed the excellent capacity（10.05 mg/g）of gaseous arsenic.The particle size and the arsenic capacity were both in the best state when the ball milling time is 4 h.Under the optima l conditions,the influence of simulated flue gas composit ion（SO₂,CO₂,O₂,NO）on the adsorption capacity for 1%Mn-ATP was investigated.The results showed that O₂ as an oxidant had a significantly promotion effect on the conversion of As（Ⅲ）to As（Ⅴ）,which was beneficial to increase the arsenic remova l capacit y and reduce the toxicit y of arsenic.SO₂ may be adsorbed on the surface of the adsorbent and form HSO₄^-or SO₄^2-when SO₂ and H₂O coexisted.This was beneficia l for As adsorption.CO₂ showed an inhibitory effect on the adsorbent’s ability to capture arsenic.For NO,the effect on As removal was not obvious.In order to further study the stability of the adsorbent and the fixat ion effect on arsenic,TC LP leaching test and microwave-assisted sequentia l extraction experiment were also carried out.The results found that 1%Mn-ATP had a good stabilization and fixation effects on arsenic compared with the tradit ional adsorbed（calcium oxide）.The toxic leaching rate of 1%Mn-ATP was 39.6%.Sequentia l extraction experiments demonstrated that the percentage of As in F1-F3 was only28.6%,while the percentage of F5 was up to 65.8%.