天然海水环境下离子浓度对MICP反应的影响

Effect of ion concentration on MICP reaction in natural seawater environment

微生物岩土技术通过生物矿化过程改善基础材料的力学性质,使其更适用于建筑或解决多学科领域的环境问题。微生物矿化过程中产生的碳酸钙是改善基础材料力学性质的主要成分,但其生成量及形态等受多种因素的影响。通过离子计、pH计、SEM、EDS和XRD等手段探究天然海水和去离子水环境在矿化过程中氯化钙和尿素浓度、比例及菌液和胶结液(氯化钙、尿素)体积比等因素对沉淀物质形貌及晶体组成的影响。结果表明:钙离子和尿素浓度及比例低时,碳酸钙的产率较高,但当初始钙离子、尿素浓度超过1.0 mol/L时,离子浓度增大对细菌产脲酶有抑制作用,浓度越高对脲酶的抑制作用越明显,沉淀物产率也随之减小,海水环境总体沉淀量与沉淀效率均高于去离子水环境。菌胶结液体积比去离子水中为1∶4、海水中不高于1∶10时,碳酸钙生成量较高,去离子水环境晶型以方解石为主,海水环境晶型以球霰石为主且沉淀中含有镁盐。

Microbial geotechnical technology improves the mechanical properties of basic materials through the process of biological mineralization,making it more suitable for building or solving environmental problems in multi-disciplinary fields.Calcium carbonate produced by microbial mineralization is the main component that improves the mechanical properties of basic materials,but the production efficiency and form are affected by many factors.By means of ion meter,pH meter,SEM,EDS and XRD,the influences of the concentration and proportion of calcium chloride and urea and the volume ratio of bacteria liquid and cementation liquid(calcium chloride,urea)on the morphology and crystal composition of precipitates in natural seawater and deionized water environment during the mineralization process were investigated.The results showed that:production of calcium carbonate is poorer when calcium ion concentration and the ratio of Ca2+to urea are lower,however,the ion has an inhibitory effect on the production of urease by bacteria when the initial calcium ion and urea concentration exceeds 1.0 mol/L.The more obvious inhibition effect was observed at a higher ion concentration,and thus a lower precipitation product rate.The amount of precipitates and precipitation rate in the seawater environment were higher than those in the deionized waterenvironment.When the volume ratio of bacterial to cementation solutions are 1∶4 in deionized water and less than 1∶10 in seawater,the amount of calcium carbonate is higher.The crystal type in deionized water is mainly calcite,while the crystal type in seawater is mainly of magnesium salt type.