Selective immobilization of Pb(II) by biogenic whewellite and its mechanism

Abstract

The development of bio-adsorbents with highly selective immobilization properties for specific heavy metals is a great challenge, but has important application value. Biogenic whewellite (BW) with high selectivity for Pb(II) was synthesized by mineral microbial transformation. The selective immobilization properties and mechanism of BW for Pb(II) were analyzed by combining mineral characterization technology and batch adsorption research methods. The results indicated that BW can efficiently and selectively immobilize Pb(II) in single or composite heavy metal adsorption solutions, and the immobilized Pb(II) is difficult to desorb. BW undergoes monolayer adsorption on Pb(II), Qmax ≈ 1073.17 mg/g. The immobilization of Pb(II) by BW is a physico-chemical adsorption process with spontaneous heat absorption and an accompanying increase in entropy. In addition, the sequestration of Pb(II) by BW remains around 756.99 mg/g even at pH = 1. The excellent selective immobilization properties of BW for Pb(II) are closely related to its smaller Ksp, electrostatic repulsion effect, organic-inorganic composite structure, acid resistance and the formation of Pb(II) oxalate. This study provides beneficial information about the recycling of lead in acidic lead-containing wastewater and composite heavy metal contaminated water bodies.