Effective immobilization of arsenic in waters and sediments using novel zirconium-loaded lanthanum-modified bentonite capping

Enhanced remediation of As(iii) and As(v) by new zirconium-loaded attapulgite and its mechanisms in the aquatic environment

“…25 As for other passivation materials (Table S4†), 30 d aluminum sulfate (ALS), 32 d LMB, 60 d Ca(NO 3 ) 2 and 30 d Zr-LMB capping reduced dissolved As by 51.1, 31.9, 47.7 and 58.0% in the depths of −20, −50, −50 and −20 mm, respectively, while 30 d Zr-ATP could reduce dissolved As by 72.9% in the depth of −80 mm below the SWI. Compared with previous studies, 50 the maximum reduction efficiencies of new Zr-LMB capping in As-polluted sediments (0, 10 and 20 mg kg −1 ) were only 58.0, 74.4 and 67.5% in the depth range of 0–20 mm below the SWI. The results clearly indicated that new Zr-ATP capping agents had more excellent passivation effects on dissolved As of sediments when compared with raw ATP, Zr-LMB and dredging technology.…”

“…All these parameters have clearly demonstrated that the Zr-ATP adsorption performance to As( v ) was stronger than As( iii ). The adsorption difference between As( v ) and As( iii ) complied with that of other adsorbents such as mesoporous magnetic ferrum–yttrium binary oxide, 58 hydrated iron oxide-loaded attapulgite 37 and zirconium-loaded LMB (Zr-LMB), 50 which is probably related to the form of As at the general environmental pH. Arsenite mainly exists as neutral H 3 AsO 3 molecules, while As( v ) mainly exists as negatively charged anions.…”

“…Batch experiments on the adsorption kinetics, isotherm and effect of pH on the adsorption of new Zr-ATP to As( iii )/As( v ) were carried out based on previous studies. 50 This study further explored the effects of anions, cations and humic acid on Zr-ATP adsorption efficiencies to As. The Zr-ATP of 50 mg was added into 20 mL solutions containing 100 μg L −1 As( iii )/As( v )(pH = 7.0) and different co-existing concentrations of HCO 3 − (NaHCO 3 , 0–360.00 mg L −1 ), SO 4 2− (Na 2 SO 4 , 0–4.50 g L −1 ), Cl − (NaCl, 0–15.00 g L −1 ), SiO 3 2− (Na 2 SiO 3 ·9H 2 O, 0–25.00 mg L −1 ), PO 4 3− (NaH 2 PO 4 ·2H 2 O, 0–5.00 mg L −1 ), Na + (NaCl, 0–100.00 mg L −1 ), K + (KCl, 0–40.00 mg L −1 ), Mg 2+ (MgCl 2 , 0–60.00 mg L −1 ), Ca 2+ (CaCl 2 , 0–200.00 mg L −1 ) and humic acid (0–18.00 mg L −1 ).…”

“…The microcosms were pumped with air, and overlying waters were resupplied every 3 days to keep the original volume due to the loss of natural evaporation. Following 60-day pre-incubation, 50 each level of As-polluted microcosms was divided into three groups: control treatment (abbreviated as CK), ATP capping and Zr-ATP capping. Powdery raw ATP and Zr-ATP were sprayed evenly on the surface sediment at a dose of 1000 capping agents/As total (mass ratio).…”

“…The adsorption efficiency ( E ) and adsorption amount ( q t ) or ( q e ) of Zr-ATP to As were calculated based on the published equations. 28,50 The adsorption kinetics and isotherm models were referred to the study of Shehzad 54 (ESI† Text S1).…”