Mechanisms of polystyrene nanoplastics adsorption onto activated carbon modified by ZnCl2.

In this study, the adsorption capacity of activated carbon was enhanced after zinc chloride activation. The effects of pore filling, n-π and π-π interaction and electrostatic interaction on the adsorption of polystyrene nanoplastics (PSNPs) by activated carbon were determined by SEM, BET, Raman spectrum, FTIR and surface Zeta potential. Pore filling, electrostatic interaction and n-π interaction and π-π interaction all played a role in the adsorption process, but n-π interaction and π-π interaction was not the decisive role. The adsorption of PSNPs on activated carbon conformed to the pseudo-second-order kinetics and Langmuir isotherm, and there was spontaneous physical adsorption process driven by entropy in the adsorption process. Further, the effects of common anions SO42-, HCO3-, and Cl- in water on the adsorption of PSNPs by activated carbon were investigated, and the results showed that the presence of these ions could increase the adsorption capacity to some extent. ZCAC has a stable adsorption capacity under tap water, but its adsorption capacity is affected under lake water. In addition, the reuse of activated carbon was investugated, and the adsorption capacity of activated carbon was fully recovered after high temperature calcination. This study provided a direction for materials modification of adsorbed nanoplastics and a feasible method for removal of nanoplastics in drinking water treatment plants.

Activation of O2 by zero-valent zinc assisted with Cu(II) for organics removal: Performance and mechanism.

This study proposes a method to activate O2 by accelerating the corrosion process for zero-valent zinc (ZVZ) with the assistance of Cu(II), promoting the consecutive production of reactive oxygen species. The mechanisms for reactive oxygen species generation are clarified with metronidazole (MTZ) as the targeted pollutant. The outcome suggests the association of Cu(Ⅱ) and ZVZ presents an apparent cooperative activity, an enhancement of 85% in MTZ removal is attained for the ZVZ/Cu(Ⅱ) system after 10 min compared to that for ZVZ. Analysis of the mechanisms involved indicates that this improvement is due to the addition of Cu(Ⅱ), which can accelerate the corrosion of ZVZ. In addition, quenching experiments and electron paramagnetic resonance (EPR) technology show that superoxide radicals (·O2-) result in rapid MTZ degradation. The primary component that is liable for O2 activation and a certain amount of H2O2 generation is verified to be ZVZ. Moreover, Cu(I) is detected in the ZVZ/Cu(Ⅱ) system, which arises from a direct reduction pathway driven by ZVZ and an indirect reduction pathway driven by active hydrogen atoms.

Enhanced removal of polyethylene terephthalate microplastics through polyaluminum chloride coagulation with three typical coagulant aids.

Given the discovery and hazard of microplastics in freshwater environments, the removal of microplastics in drinking water deserves more attention. Nevertheless, in the light of existing literature, the effectiveness of conventional coagulation on microplastics removal is insufficient. Hence, enhanced coagulation is worth being explored. This study investigated the improving performance of anionic polyacrylamide (PAM), sodium alginate (SA), and activated silicic acid (ASA) when using poly­aluminum chloride (PAC) to remove polyethylene terephthalate (PET) microplastics. The experimental results showed that ASA had the highest removal efficiency (54.70%) under conventional dosage, while PAM achieved the best removal effect (91.45%) at high dosage. Mechanism of coagulation was studied by scanning electron microscope (SEM), Fourier transform infrared spectroscope (FTIR), X-ray photoelectron spectroscopy (XPS), and the results illustrated that when only PAC existed or the dosage of coagulant aids was low, double layer compression was the main principle. The increase of coagulant aids dosage improved the effect of adsorption and sweep flocculation significantly. Moreover, jar tests carried in different conditions demonstrated that the current coagulation systems were highly adaptable.