Contribution of Soluble Minerals in Biochar to Pb2+ Adsorption in Aqueous Solutions

Abstract

Biochar is widely used as an adsorbent to remove heavy metals from aqueous solutions. To investigate the contribution of soluble minerals (mainly anions) to Pb 2+ removal in solution, wheat straw biochar was washed with deionized water to remove soluble minerals. Batch adsorption was conducted using washed biochar (WBC) and unwashed biochar (BC) to absorb Pb 2+ . After washing, the pH and ash content of biochar were reduced, while the specific surface area and total pore volume were increased. Adsorption kinetics of Pb 2+ onto BC and WBC were well fitted to the pseudo-second-order model (R 2 > 0.99). Pb sorption on BC and WBC were better fit with the Langmuir model (R 2 = 0.96 to 0.97) than the Freundlich model (R 2 = 0.71 to 0.87). The Langmuir maximum adsorption capacity of Pb on BC was 99.7 mg g -1 , which was 4.5-fold higher than that on WBC when the initial solution pH was 5.0. The concentration of SO4 2-, CO3 2-, SiO3 2-, and PO4 3-in the equilibrium solution was reduced by 69, 89, 97, and 41%, respectively, with the increase of initial Pb 2+ concentration. The difference of Pb 2+ adsorption capacity between BC and WBC proved that the soluble anions in biochar play an important role in Pb 2+ sorption onto biochar.

Treatment of mine water for the fast removal of zinc and lead by wood ash amended biochar

“…Mobile divalent Pb species shift to immobile lead carbonate and hydroxide forms which dominate speciation causing Pb precipitation and capture by WAS. The formation of lead carbonates, such as Pb(CO 3 ) modelled by PHREEQC, have been seen to be related to the high alkalinity of the biochar and soluble carbonate, sulphate and phosphate anions 57,58 . Regular sampling of Nantymywn has shown sulphate concentration to be as high as 11 mg/L adding substantially more anions into the system possibly playing a role in Zn and Pb speciation and further increasing the formation of precipitates 48,59 .…”

“…The formation of lead carbonates, such as Pb(CO 3 ) modelled by PHREEQC, have been seen to be related to the high alkalinity of the biochar and soluble carbonate, sulphate and phosphate anions. 57,58 Regular sampling of Nantymwyn has shown sulphate concentration to be as high as 11 mg L À1 adding substantially more anions into the system possibly playing a role in Zn and Pb speciation and further increasing the formation of precipitates. 48,59 Given the right conditions, as the addition of WAS to the Nantymwyn system provides, precipitation is a rapid process.…”

Multiple Characterization for Mechanistic Insights of Pb(II) Sorption onto Biochars Derived from Herbaceous Plant, Biosolid, and Livestock Waste

“…Pb(II), one of the most investigated metal ions adsorbed by biochars (Ding et al 2016a;Inyang et al 2016;Chen et al 2017), was selected as a represented heavy metal ion. Batch isotherm and kinetic sorption experiments were performed.…”

Developing motorway balancing ponds with long-term net ecological value

“…Mobile divalent Pb species shift to immobile lead carbonate and hydroxide forms which dominate speciation causing Pb precipitation and capture by WAS. The formation of lead carbonates, such as Pb(CO3) modelled by PHREEQC, have been seen to be related to the high alkalinity of the biochar and soluble carbonate, sulphate and phosphate anions (Chen et al 2016;Zhang et al 2017b). Regular sampling of Nantymywn has shown sulphate concentration to be as high as 11 mg/L adding substantially more anions into the system possibly playing a role in Zn and Pb speciation and further increasing the formation of precipitates (Dean et al 2005;Natural Resources Wales 2021).…”