Enhancing calcium carbonate production and distribution by using soybean urease to reinforce loess
Dequan Kong,Muhammad Muneer,Rong Wan,Xinyang Liu,Masood ur Rahman,Shihao Gu,Mouhong Wang,Muhammad Shahbaz
Abstract
The study optimizes enzyme-induced carbonate precipitation (EICP) using crude soybean urease to improve calcium carbonate yield and distribution for efficient, sustainable loess stabilization. The effects of temperature (−10 - 50C), soybean powder concentration (30 - 150 g/L), and reaction time (3 - 48 h) on urease activity were quantified using the phenol–sodium hypochlorite colorimetric method. Calcium carbonate yield and distribution were evaluated through acid pickling under varying calcium sources (chloride, nitrate, acetate), concentrations (0.5–2.0 mol/L), and spraying cycles (1–4). Results show that urease activity declines most sharply within 3–12 h and calcium carbonate yield increases linearly with spraying frequency; calcium nitrate (16.1% at 0.5 mol/L), calcium chloride (9.2%), and calcium acetate (9.3%). Surface-layer precipitation decreases with additional sprays, while middle and deep layers exhibit significant gains (chloride: 195.35%, nitrate: 219.32%, acetate: 224.56%). Calcium acetate is best for deep reinforcement, calcium chloride for rapid surface stabilization, and calcium nitrate for balanced performance. Since measuring urease activity in water is easier and more accurate than in soil, this study develops a regression model to predict soil urease activity from water-based tests. These findings guide optimal material and method selection for effective EICP-based loess stabilization.
Dequan Kong, Muhammad Muneer, Xinyang Liu, Masood ur Rahman, Shihao Gu, Mouhong Wang — School of Civil Engineering, Chang'an University, Xi'an, 710061, China
Muhammad Shahbaz — College of Civil and Transportation Engineering, Shenzhen University, Shenzhen, 518060, China
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