大豆脲酶诱导碳酸钙沉淀的多因素影响分析

本文探究了多个影响因素对大豆脲酶诱导碳酸钙沉淀(SICP)的影响,以优选出主要影响因素并提供其最佳范围。首先分析了脲酶浓度和温度对脲酶活性的影响;之后通过正交实验设计,进行25种工况的SICP水溶液实验,研究不同因素组合下Ca²⁺利用率的变化规律;最后借助扫描电子显微镜观测不同工况下生成碳酸钙的形态。结果表明:低温有利于脲酶的保存及活性发挥,5 ℃时脲酶活性能保持21 d以上;同一温度下,脲酶浓度越大,脲酶初始活性越高,脲酶完全失活所需时间越短。pH值、脲酶与胶结液体积比是影响Ca²⁺利用率的主要因素。为达到较高的Ca²⁺利用率,脲酶和胶结液最佳体积比为1,氯化钙与尿素最佳浓度比为1.5,Ca²⁺最佳浓度为1 mol/L。当脲酶浓度较低时生成的六面体状碳酸钙较多;随着脲酶浓度的增大,所沉淀的碳酸钙向球形转变。大豆中富含的天冬氨酸是控制碳酸钙形态的重要因素。

Affecting Analysis of Multi-Factors on Soybean Urease-Induced Calcium Carbonate Precipitation

The effects of multiple influencing factors on soybean urease-induced calcium carbonate precipitation (SICP) were explored to select the main influencing factors and provided their optimal ranges. Firstly, the influence of urease concentration and temperature on urease activity were analyzed. After that, based on orthogonal test design, 25 test conditions of SICP aqueous solution tests were conducted, and the variation law of Ca²⁺ utilization ratio was studied through the combination of different factors. Also the morphology of CaCO₃ was observed with SEM in diverse test conditions. The results show that low temperature delivers benefits to urease preservation and its activity exertion, urease activity can be preserved over 21 d with 5 ℃. At the same temperature, the greater the urease concentration is, the higher the initial activity of urease boasts and the shorter the time required for complete inactivation of urease. The pH value and the volume ratio of urease to cementation solution are the main factors affecting the Ca²⁺ utilization ratio. In order to achieve a higher Ca²⁺ utilization ratio, the optimum volume ratio of urease to cementation solution could be 1 while the optimal concentration ratio of CaCl₂ to urea is 1.5, and the best Ca²⁺ concentration is 1 mol/L. More hexahedral CaCO₃ is produced, when the urease concentration is low, and the shape of precipitated CaCO₃ turns into spherical as the urease concentration increases. Aspartic acid which is rich in soybeans, is an significant factor in controlling the form of CaCO₃.