Research On New Dust-depressor Of Calcite Precipitation Induced By Microbe And Enzyme

Dust pollution is increasingly severe and produces lots of harm,including destroying ecological environment and influencing human health.The dust control has been taken seriously.Chemical dust-depressors restrain dust rising by adhesion,wetting and aggregation,which are considered to be the best way to solve the dust pollution.However,chemical dust-depressors also bring some adverse effects to the environment,such as reentrainment,secondary pollution caused by refractory component,corrosion,threatening plants and soil.At present,there are few reports on environmentally friendly and effective dust-depressor.Thus,it is of great significance to develop and evaluate the green dust-depressor,which is important to the atmospheric environment.The road dust of Nanjing,Suzhou and Nantong are chosen as the research objects,ignition loss and element content of different road surfaces are analyzed.The results show that the road dust of Suzhou has the highest ignition loss on account of many organic and volatile components.Soil dust is the primary source of Nanjing,Suzhou and Nantong road dust.Construction dust is the second source and has great influence on Nanjing and Nantong except Suzhou.Compared with Suzhou and Nantong,coal ash has the greatest impact on Nanjing.Environment friendly microbial dust-depressor and urease dust-depressor have been developed utilizing a method of microbial inducing calcite precipitation（MICP）.MICP has the characteristics of non-toxic,degradable,great bondbehavior and eco-compatible.The suitable environment and best proportions of microbial dust-depressor and urease dust-depressor are investigated.The results show that both of the depressors are suitable for high temperature and neutral environment.Urease dust-depressor is applicable to wider pH range.The best proportion of microbial dust-depressor is OD600=1.5 of sporosarcina pasteurii,0.8 mol?L^-1 of urea and 0.8mol?L^-1 of CaCl₂.The best proportion of urease dust-depressor varies with the temperature(at 5℃,35 g·L^-1 of urease,0.8 mol?L^-1 of urea,0.8 mol?L^-1 of CaCl₂;at 25℃,40 g·L^-1 of urease,0.6 mol?L^-1 of urea,0.6 mol?L^-1 of CaCl₂;at 35℃,30 g·L^-1 of urease,0.8 mol?L^-1 of urea,0.8 mol?L^-1 of CaCl₂,1 g?L^-1 of SAP;at 45℃,30 g·L^-1 of urease,0.6 mol?L^-1 of urea,0.6 mol?L^-1 of CaCl₂,4 g?L^-1 of SAP).Pure water,CaCl₂ and SAP are chosen to compare with microbial dust-depressor and urease dust-depressor on the performance.The results show that urease dust-depressor possesses 0.038 g·m^-2·s^-1 of evaporation rate,26.013%of driage.Urease dust-depressor possesses the best performance of evaporation and water retentivity while microbial dust-depressor is poor.Urease dust-depressor and microbial dust-depressor are superior to the other 3 dust-depressors on the performance of wind resistance and dust suppression efficiency.Urease dust-depressor possesses the best wind resistance index of 27.844,while microbial dust-depressor possesses the highest dust suppression efficiency（79.119%）.Urease dust-depressor and microbial dust-depressor both have a greater penetration rate and microbial dust-depressor possesses the highest penetration rate(3.13 mm·min^-1).The mass-loss rates of 5 dust-depressors are above 90%,so all dust-depressors have poor performances on the rain resistance.Both urease dust-depressor and microbial dust-depressor are superior to the other 3 dust-depressors on the performance of freezing resistance and microbial dust-depressor possesses the highest compressive strength（41.4N）.Urease dust-depressor have a greater heat resistance while microbial dust-depressor has poor performance.Urease dust-depressor is best on the performance of material pile test and microbial dust-depressor is the second.In field trials,urease dust-depressor and microbial dust-depressor have better performance on the control of PM1.0,PM2.5 and PM10.Urease dust-depressor exhibits better restraining time than that of microbial dust-depressor,while microbial dust-depressor displays better restraining effect than that of urease dust-depressor.Microbial dust-depressor has the best restraining effect on the control of particles（≤1.0 um）,reducing 243655particles（≤1.0 um）during the testing period.Urease dust-depressor has the best restraining effect on the control of particles（≤10 um）,reducing 2465 particles（≤10 um）during the testing period.