Extraction of urease from soybean for preparing biocement: Laboratory study

The soybean urease-induced carbonate precipitation (SUICP) is proposed as a novel biocement for the treatment of nickel contaminants and cementation of sandy soil because of the high cost of cultivating urease-producing bacteria (UPB). The best soaking time and content of soybean powder are separately 30 minutes and 130 g/L according to 5 U of urease activity standard. When the best mass ratio of urea to nickel ions to soybean powder filtrate (SPF) is 1:2.4:20, the removal efficiency of nickel ions is the best. For treating 1 L of nickel ion solution (1200 mg/L), the removal efficiency of nickel ions can reach 89.42% in the best mass ratio. The removal efficiency of nickel ions is 99.33% under the best mass ratio in the incinerated bottom ash (IBA). In biocemented sandy soil, the average unconfined compressive strength (UCS) of sand blocks cemented through the soybean urease-based biocement can reach 118.89 kPa when cementation levels are three. Currently, the average content of CaCO 3 was 2.52% in sand blocks. As a result, the SUICP process can be applied to remove heavy metal ions in wastewater or solid waste and improve the mechanical properties of soft soil foundations.