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

Lin Wang,Zhong-Fei Xue,Wen-Chieh Cheng

doi:10.3389/fbioe.2022.849631

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.

Highlights

Heavy metal contamination raises sustainable concerns and causes threats to human health and plants (Kumari et al, 2016; Jiang et al, 2019; Rahman et al, 2020; Chen et al, 2021a; Tan et al, 2022)
Ammonium ions (NH4+) and hydroxide ions (OH−) are known to be discharged after urea hydrolysis, and NH4+ and pH are considered as the key indicators of describing the degree of urea hydrolysis (Fisher et al, 2017; Sun et al, 2021)
In biomineralization, attending higher degrees of urea hydrolysis is considered of great necessity to improve heavy metal remediation efficiency

Summary

Introduction

Heavy metal contamination raises sustainable concerns and causes threats to human health and plants (Kumari et al, 2016; Jiang et al, 2019; Rahman et al, 2020; Chen et al, 2021a; Tan et al, 2022). In the past few decades, remediation methods including replacement, soil flushing, electrokinetic remediation, chemical precipitation, ion exchange, and phytoremediation were developed (Mena et al, 2016; Kumari et al, 2017; Kumari et al, 2018; Chen and Achal, 2019; Duarte-Nass et al, 2020; Ahenkorah et al, 2021; Hu L. et al, 2021; Jiang et al, 2021) They are usually time-consuming and may cause secondary pollution (Achal et al, 2012; Nancharaiah et al, 2016; Kappaun et al, 2018; Xue et al, 2022; Yan et al, 2021; Duan et al, 2021a; Cheng et al, 2021; Duan et al, 2021b). Enzyme-induced carbonate precipitation (EICP) is a novel biogeotechnical technique and has been widely applied to strengthen calcareous sands

Objectives

Methods

Results

Conclusion