The Effect of Calcium Source on Pb and Cu Remediation Using Enzyme-Induced Carbonate Precipitation

Abstract

Heavy metal contamination not only causes threat to human health but also raises sustainable development concerns. The use of traditional methods to remediate heavy metal contamination is however time-consuming, and the remediation efficiency may not meet the requirements as expected. The present study conducted a series of test tube experiments to investigate the effect of calcium source on the lead and copper removals. In addition to the test tube experiments, numerical simulations were performed using Visual MINTEQ software package considering different degrees of urea hydrolysis derived from the experiments. The remediation efficiency degrades when NH4+ and OH− concentrations are not sufficient to precipitate the majority of Pb2+ and Cu2+. It also degrades when CaO turns pH into highly alkaline conditions. The numerical simulations do not take the dissolution of precipitation into account and therefore overestimate the remediation efficiency when subjected to lower Pb(NO3)2 or Cu(NO3)2 concentrations. The findings highlight the potential of applying the enzyme-induced carbonate precipitation to lead and copper remediations.

Effects of the Urease Concentration and Calcium Source on Enzyme-Induced Carbonate Precipitation for Lead Remediation

“…Given that K sp (Ca(OH) 2 ) being 5.5 × 10 –6 is greater than K sp (Pb(OH) 2 ) being 1.2 × 10 –15 , Ca(OH) 2 tends to transform to Pb(OH) 2 . However, Pb(OH) 2 is deemed soluble when exposed to alkaline environments ( Edwards et al, 1992 ; Baltpurvins et al, 1996 ; Vítková et al, 2009 ; and Wang et al, 2022 ). When Pb(OH) 2 is just formed following the aforesaid transformation, and it is also on the way to dissolve, thereby releasing the Pb ions into the solution.…”

Effect of seepage conditions on the microstructural evolution of loess across north-west China

“…The two ends converge to give an aggressive control of land degradation. According to the finding of this work, biomineralization technology may be used to precipitate calcium carbonate through catalyzing urea hydrolysis using the ureolytic bacteria ( Hu et al., 2021b ; Xue et al., 2022 ; Wang et al., 2022a , c ). The precipitation of calcium carbonate not only impedes the dissolution of calcite by the dolomitization but also reduces rates of land degradation.…”

Treatment of engineering waste slurries by microbially induced struvite precipitation mechanisms

“…Second, urease is generated during the process of microorganic metabolism and catalyzes the hydrolysis of nitrogen-containing compounds to NH + 4 via Eqs 1-3, which is conducive to the production of MAP (MgNH 4 PO 4 • 6H 2 O) (Eq. 4) (Yu et al, 2021;Wang et al, 2022b). A previous study reported that MAP could be precipitated by adding NaOH to adjust the pH of the system (Yao, 2006), while the generated alkaline MAP could seriously damage the soil and, thus, limit its potential as a compound fertilizer for agriculture (Leng and Soares, 2021).…”