The effect of solvent-conditioning on soil organic matter sorption affinity for diuron and phenanthrene

A new function of spent activated carbon in BAC process: Removing heavy metals by ion exchange mechanism

To investigate the potential of the spent activated carbon (AC) on removing heavy metals, the spent ACs used 5 years were collected from a full-scale BAC water treatment plant of southern China. The study found that the spent ACs had very good adsorption capacity for Pb(II) and Cd(II) at low concentrations (about 200 μg/L or less) with the maximum removal rates of more than 95% and 86% respectively (only 10-15% for virgin ACs), which will provide the theoretical basis for the disposal of spent AC (the hazardous waste) in BAC process or the combination reuse of spent AC and the virgin AC. Surface properties analyses showed that compared to virgin AC, the pH and PZC in the spent AC significantly decreased, and the relative abundance of surface carboxyl increased by 81% on average, which are essential for the adsorption of metals. To explore the adsorption mechanism, take Pb(II) for example, the adsorption isotherm and kinetics fittings were carried out, which can be well described by Freundlich model (R² = 0.9356) and the pseudo-second-order kinetic model (R² = 0.9276), respectively. Analyses of influencing factors, FT-IR and XPS before and after Pb(II) adsorption confirmed the ion exchange mechanism of spent AC for the removal of heavy metals.

Spatial distribution of organic pollutants in industrial construction and demolition waste and their mutual interaction on an abandoned pesticide manufacturing plant

A comprehensive field investigation of organic pollutants was examined in industrial construction and demolition waste (ICDW) inside an abandoned pesticide manufacturing plant. Concentrations of eight types of pesticides, a metabolite and two intermediates were studied. The ICDW was under severe and long-term contamination by organophosphorus, intermediates and pyrethroid pesticide with mean concentrations of 23,429, 3538 and 179.4 mg kg(-1), respectively. FT-IR analysis suggested that physical absorption and chemical bonding were their mutual interaction forms. Patterns of total pesticide spatial distribution showed good correlations with manufacturing processes spreading all over the plant both in enclosed workshops and in residues randomly dumped outside, while bricks and coatings were the most vulnerable to pollutants. Ultimately the fate of the OPPs was diversified as the immersion of ICDW in water largely transferred the pollutants into aquatic systems while exposure outside did not largely lead to pesticide degradation. The adoption of centralized collections for the disposal of wastes could only eliminate part of the contaminated ICDW, probably due to lack of knowledge and criteria. Correlation matrix and cluster analysis indicated that regulated disposal and management of polluted ICDW was effective, thus presenting the requirement for its appropriate disposal.

Sorption affinities of sulfamethoxazole and carbamazepine to two sorbents under co-sorption systems

The Kd of sulfamethoxazole (SMX) on activated carbon (AC) was larger than that of SMX on single-walled carbon nanotubes (SC), but the competition of SMX with carbamazepine (CBZ) for adsorption sites was weaker on AC than SC. Thus, a large Kd value does not necessarily reflect a high affinity. The analysis of the apparent sorption, competition, desorption hysteresis, and the sorption thermodynamics for SMX and CBZ did not provide sufficient information to distinguish their sorption affinities. The release of the adsorbed CBZ was not altered with SMX as the competitor, but SMX release increased significantly after CBZ addition. The higher sorption affinity of CBZ may be explained by the interactions of the CBZ benzene rings with the aromatic structures of the adsorbents. Although the thermodynamic meaning cannot be described, the release ratio of the adsorbed pollutants provides useful information for understanding pollutant sorption strength and associated risks.