Variable charges of a red soil from different depths: Acid-base buffer capacity and surface complexation model

Peng

Bull Environ Contam Toxicol

et al. 2019

Self Cite

To investigate the aging process and reduction of Cr(VI) in two soils. The adsorption behavior of the soils demonstrated that the paddy soil had higher adsorption capacity for Cr(VI), but the capacity was lower for Cr(III), which contrasted the results for fluro-aquic soil. The mobilizable Cr was assessed using EDTA extraction. The results suggested that the reduction of Cr(VI) to Cr(III) and the aging process occurred simultaneously. A simplified kinetic model was established and the rate constants of the reduction and aging processes were obtained. The aging process and reduction of Cr(VI) were faster in the paddy soil, due to a higher adsorption capacity and stronger reducing ability, as indicated by the organic matter and amorphous Fe oxides. The Cr(III) aging was faster in the fluro-aquic soil due to the low solubility of Cr(III) at a high pH. The modeling study provides a fundamental understanding of the dynamics of Cr mobility in a complicated soil system.

Section: Methodsmentioning

confidence: 99%

The Kinetics of Aging and Reducing Processes of Cr(VI) in Two Soils

Peng

Bull Environ Contam Toxicol

et al. 2019

Self Cite

“…To prepare iron-rich particles, red soil was sampled from about 1 m below the surface of a plantation located in South China (N23°27′47″, E114°33′11″). The Fe content of the red soil was approximately 13.5%; details of the elemental and mineral composition of the red soil can be found in Wang et al 26 The soil sample was sterilized by autoclaving, air-dried, and then ground to reduce the particle size. Colloidal particles less than 10 μm were separated by wet-sieving through a 1500-mesh sieve.…”

Section: Preparation Of Iron-rich Particlesmentioning

confidence: 99%

Immobile Iron-Rich Particles Promote Arsenic Retention and Regulate Arsenic Biotransformation in Treatment Wetlands

Liu

Häggblom

et al. 2022

Environ. Sci. Technol.

Remediation of arsenic (As)-contaminated wastewater by treatment wetlands (TWs) remains a technological challenge due to the low As adsorption capacity of wetland substrates and the release of adsorbed As to pore water. This study investigated the feasibility of using immobile iron-rich particles (IIRP) to promote As retention and to regulate As biotransformation in TWs. Iron-rich particles prepared were immobilized in the interspace of a gravel substrate. TWs with IIRP amendment (IIRP-TWs) achieved a stable As removal efficiency of 63 ± 4% over 300 days, while no As removal or release was observed in TWs without IIRP after 180 days of continuous operation. IIRP amendment provided additional adsorption sites and increased the stability of adsorbed As due to the strong binding affinity between As and Fe oxides. Microbially mediated As(III) oxidation was intensified by iron-rich particles in the anaerobic bottom layer of IIRP-TWs. Myxococcus and Fimbriimonadaceae were identified as As(III) oxidizers. Further, metagenomic binning suggested that these two bacterial taxa may have the capability for anaerobic As(III) oxidation. Overall, this study demonstrated that abiotic and biotic effects of IIRP contribute to As retention in TWs and provided insights into the role of IIRP for the remediation of As contamination.

“…The surface complexation models (SCMs) are mainly used to study the chemical reactions occurring at the solid-liquid interface. Hydroxy proton transfer occurs in the aqueous solution, some located on the surface of the metal are called Lewis acid, and others losing protons are called Lewis base, both of which react with ligands in the solution [16,17] . Protonation and deprotonation of surface functional groups on the material make a significant contribution to the acid-base buffering capacity.…”

Section: Introductionmentioning

confidence: 99%

Differential removal of tetracycline hydrochloride and quinolone antibiotics by calcined and uncalcined layered double hydroxides

Zhang¹,

García‐Meza²,

Li³

2023

Miner Miner Mater

Antibiotics generally cause drug-resistant genes (ARGs) and drug-resistant bacteria (ARBs). With a complex class of antibiotics, it is very crucial to select specific adsorbents for different kinds of antibiotics. Zn-Al layered double hydroxide (LDH) and calcined layered double hydroxide (LDO) were prepared as absorbents for tetracycline hydrochloride (TCH) and ofloxacin (OFX), which were two antibiotics with different structures. According to the results of the adsorption experiments, LDO has the best adsorption capacity on TCH, reaching 322.58 mg/g. Acid-base titration, XRD, TEM, SEM, BET, and FI-TR analyses indicate that LDO has more active sites on the surface, the “memory effect”, and a larger specific surface area. In contrast, the removal rate of OFX by LDO is low because OFX has a more stable quinolone ring structure. Furthermore, after five adsorption-desorption cycles, the adsorption rate of TCH remains at 94.9%, demonstrating that LDO has good cyclic adsorption capacity for TCH. This study creatively combines acid-base buffering characteristics to study the mechanism of the adsorption of antibiotics by hydrotalcite, and proposes that LDO can be used as a special adsorbent for TCH.