Highly-efficient peroxydisulfate activation by polyaniline-polypyrrole copolymers derived pyrolytic carbon for 2,4-dichlorophenol removal in water: Coupling mechanism of singlet oxygen and electron transfer.

Carbonization of N-containing aromatic polymers is a promising route to prepare N-doped carbon materials with low cost, easy regulation, and no external N source. However, there are relatively few studies applying these materials for persulfate activation, and the catalytic mechanisms of the existing reaction systems are divergent. In this paper, a series of N-doped carbon materials were prepared by carbonizing polyaniline (PANI), polypyrrole (PPy), and PANI-PPy copolymers. The copolymer-derived carbon materials exhibit superior peroxydisulfate (PDS) catalytic activity compared to some commercially available and reported carbon materials. Combing quenching experiments, EPR analysis, chemical probe analysis, and various electrochemical analysis methods identified the singlet oxygen (1O2) and electron transfer as the main reaction pathways of all systems, but the contribution of each pathway was influenced by the types of precursors. The structure-activity relationship indicated that the carbonyl group (CO) was the main active site for the 1O2 pathway, while the electron transfer ability of the reaction system and the potential of the complex formed by catalyst and PDS jointly determined the electron transfer pathway. This paper provides a new strategy for obtaining excellent N-doped carbon-based persulfate activators and deepens the insight into the mechanism of PDS activation by N-doped carbon materials.

Soil washing of total petroleum and polycyclic aromatic hydrocarbons from crude oil-contaminated ultisol using aqueous extracts of waterleaf.

Ultisols are acidic soils found in humid climates and are known for poor fertility. Crude oil impacted ultisols, therefore, require special treatment measures to account for nutrient loss during treatment. In this paper, we report the utilization of a food waste, aqueous extracts of waterleaf (Talinum triangulare), as a plant-derived surfactant to wash simulated crude oil-contaminated soils. The soils before and after washing were monitored for microbial loads, nutrient parameters, physicochemical characteristics, total petroleum hydrocarbons (TPHs) and polycyclic aromatic hydrocarbons (PAHs). Although higher amounts of PAHs (up to 100%) were removed compared to TPHs (up to 95.7%), the results revealed that the efficiency of the waterleaf extracts was comparable to that of a commercial surfactant sodium dodecyl sulphate. However, soils washed with the waterleaf extracts retained some significant amounts of nutrients and favourable pH moderation. In both surfactants, soil microbial loads reduced significantly. Overall, the aqueous waterleaf extracts showed potential as ecofriendly surfactants and nutrients retainer during soil washing of contaminated ultisols.

Experimental study of viscosity modification coupled with phase transfer catalysis for enhanced remediation of non-aqueous phase trichloroethene polluted heterogeneous aquifer.

The degradation of dense non-aqueous phase liquid trichloroethene in low permeability zone is a challenging issue due to limited mass transfer between water-soluble oxidants (i.e., MnO4-) and residual phase trichloroethene and the bypassing of amendments in low permeability zone. This work accomplished trichloroethene oxidation enhancement through coupling viscosity modification by using xanthan with phase transfer of MnO4- by using phase transfer catalyst (PTC). Experiments were conducted by sand columns and 2D-tanks, and results revealed that after ~11.7 g of trichloroethene was injected in each tank, the mass of trichloroethene degradation was 1.3, 5.9, 6.9 and 8.5 g in MnO4-, MnO4- + xanthan, MnO4- + PTC and MnO4- + PTC + xanthan reaction systems, respectively. Combining PTC and xanthan with MnO4- increased the rate of continuous formation of Cl-, reflected in the acceleration of heterogeneous reactions and MnO4- transport enhancement in low permeability zone by PTC and xanthan. Moreover, PTC promoted dissolved Mn (Ⅱ) and Mn (Ⅲ) formation in the process of MnO4- reduction, and thus effectively inhibited MnO2 generation. In conclusion, the results revealed that PTC and xanthan could perform their respective contributions to mass transfer and amendment transport for jointly enhanced the remediation of trichloroethene polluted heterogeneous aquifer.

COVID-19 drugs in aquatic systems: a review.

The outbreak of the human coronavirus disease 2019 (COVID-19) has induced an unprecedented increase in the use of several old and repurposed therapeutic drugs such as veterinary medicines, e.g. ivermectin, nonsteroidal anti-inflammatory drugs, protein and peptide therapeutics, disease-modifying anti-rheumatic drugs and antimalarial drugs, antiretrovirals, analgesics, and supporting agents, e.g. azithromycin and corticosteroids. Excretion of drugs and their metabolites in stools and urine release these drugs into wastewater, and ultimately into surface waters and groundwater systems. Here, we review the sources, behaviour, environmental fate, risks, and remediation of those drugs. We discuss drug transformation in aquatic environments and in wastewater treatment systems. Degradation mechanisms and metabolite toxicity are poorly known. Potential risks include endocrine disruption, acute and chronic toxicity, disruption of ecosystem functions and trophic interactions in aquatic organisms, and the emergence of antimicrobial resistance.

Recycling anaerobic digestate enhances the co-digestion potential of agro-industrial residues: influence of different digestates as sources of microbial inoculum.

Anaerobic codigestion (AcD) of agroindustrial residues was investigated. Granular sludge from bench-scale bioreactors digesting different manure were acclimated and recycled as microbial seed sludge to demonstrate inoculum-type influence on digestion performance. The biomethane potential (BMP) assay was operated for 30 days at 40 ± 2 °C in batch-type laboratory-scale reactors (100 mL). In inoculum amended reactors, codigestion showed significant, yet distinctive, biomethanation than monodigestion with a 5-fold increase (p < 0.05) in average biogas (248.3 ± 5.30 mL gVS-1) and CH4 yield (207.5 ± 4.15 mL gVS-1). The pH, soluble chemical oxygen demand (sCOD) and volatile fatty acids (VFAs) concentrations were within limits for stable AcD process with elevated total solids (TS) and volatile solids (VS) removal efficiencies. This study reinforces advancements in the recycling of digestate in biodigesters and suggests the appropriate selection of inoculum, preferably cow manure, to essentially boost methane production from these wastes.

Anaerobic co-digestion of spent coconut copra with cow urine for enhanced biogas production.

Laboratory-scale bioreactors were used to co-digest spent coconut copra (SCC) and cow urine (CU) as a co-substrate (SCC + CU) in a batch mode under thermophilic condition (45 ± 2°C) in order to enhance biogas production. The effect of CU pretreatment on the performance indicators (biogas and biomethane yields, total solids (TS), and volatile solids (VS) reduction, pH and volatile fatty acids (VFAs) concentrations) were also examined. This was compared with mono-digestion of SCC. The experiment was performed with different mixing ratios in reactors labelled as follows: A = 75 g SCC + 5 ml CU; B = 70 g SCC + 10 ml CU; C = 65 g SCC + 15 ml CU; and D (control) = 80 g SCC at a hydraulic retention time of 42 days. Co-digestion (SCC + CU) significantly improved anaerobic digestion (AD) performance resulting in a threefold and fivefold increase in biogas and biomethane production, respectively, with concomitant TS (44.9-57.7%) and VS (55.4-60.3%) removal efficiencies. But for mono-digestion (control experiment), all CU treated and co-digestion assays showed pH stability ranging between 6.6 and 7.4 and VFAs' concentrations ranging from 15-330 mgL-1. By acting as a buffer, CU effectively enhanced the AD performance of SCC as demonstrated in this study.

Ecological risks of phenolic endocrine disrupting compounds in an urban tropical river.

The distribution of emerging organic contaminants in drinking water sources in Africa is a subject with very scanty data and information. In order to fill knowledge gaps, we report here the distribution and potential ecological risks of three phenolic compounds (bisphenol A (BPA), 4-nonylphenol (NP), and 4-tert-octylphenol (OP)), which have been previously identified to have the potential of endocrine disrupting activity, in surface water and sediment of the New Calabar River. The compounds were quantified using GC-MS. At all sampling sites, a similar concentration pattern of BPA > NP > OP was recorded, with the exception of Choba sampling station in which the levels of these endocrine disrupting compounds were low or undetectable. The levels of BPA in surface water ranged from 1.20 to 63.64 µg/L, whereas those of NP and OP ranged from < 0.20 to 2.15 µg/L and from < 0.10 to 0.68 µg/L, respectively. For sediments, measured levels were from 1.20 to 66.57 µg/kg for BPA, from < 0.35 to 3.37 µg/kg for NP, and from < 0.13 to 0.90 µg/kg for OP. Risk quotients (RQs) assessed for some sensitive organisms (algae, Daphnia magna, and fish) were above 1 for BPA and NP, whereas RQs for OP were below 1. This implies that BPA and NP at the levels detected could have potential risks to the sensitive organisms considered, but low risk for OP.