Mechanism of methylphosphonic acid photo-degradation based on phosphate oxygen isotopes and density functional theory

Phosphonate consumers potentially contributing to methane production in Brazilian soda lakes

Oxic methane production (OMP) has been reported to significantly contribute to methane emissions from oxic surface waters. Demethylation of organic compounds, photosynthesis-associated methane production, and (bacterio)chlorophyll reduction activity are some of the investigated mechanisms as potential OMP sources related to photosynthetic organisms. Recently, cyanobacteria have often been correlated with methane accumulation and emission in freshwater, marine, and saline systems. The Brazilian Pantanal is the world's largest wetland system, with approximately 10,000 shallow lakes, most of which are highly alkaline and saline extreme environments. We initiated this study with an overall investigation using genetic markers, from which we explored metagenomic and limnological data from the Pantanal soda for five potential OMP pathways. Our results showed a strong positive correlation between dissolved methane concentrations and bloom events. Metagenomic data and nutrients, mainly orthophosphate, nitrogen, iron, and methane concentrations, suggest that the organic phosphorous demethylation pathway has the most potential to drive OMP in lakes with blooms. A specialized bacterial community was identified, including the Cyanobacteria Raphidiopsis, although the bloom does not contain the genes to carry out this process. These data showed enough evidence to infer the occurrence of an OMP pathway at Pantanal soda lakes, including the microbial sources and their relation to the cyanobacterial blooms.

Selective recovery of glyphosine from glyphosate mother liquor using a modified biosorbent: Competitive substitution adsorption

Here, an easy to prepare, environmentally friendly, and highly efficient biosorbent was synthesized for the selective recovery of glyphosine from glyphosate mother liquor. Batch adsorption and continuous fixed-bed column experiments were conducted to determine its adsorption properties and evaluate its potential towards practical applications. The results showed that the biosorbent exhibited a fast adsorption rate and high adsorption capacity (296.1 mg/g) toward glyphosine. Further, the biosorbent performed better under acidic conditions, and was easily regenerated using an alkaline solution, maintaining a high removal efficiency even after 5 adsorption-desorption cycles. Competitive adsorption experiments in binary and ternary systems revealed that the biosorbent showed a higher adsorption affinity toward the target glyphosine compared with glyphosate and phosphorous acid (which are the other main constituents of glyphosate mother liquor), enabling the selective recycling of glyphosine. These observations were further supported through density functional theory (DFT) calculations of the adsorption energy. Moreover, fixed-bed column experiments showed that the prepared biosorbent could maintain its high performance in actual glyphosate mother liquor. Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) analyses revealed that the adsorption mechanism is strongly associated with electrostatic attraction and hydrogen bonding between -NH₃⁺ and glyphosine. Overall, the prepared biosorbent can be considered as an excellent candidate for the selective recovery of glyphosine from complicated industrial wastewater systems.

Adsorption and photochemical capacity on 17α-ethinylestradiol by char produced in the thermo treatment process of plastic waste

Plastic is a major component of solid waste. It is often thermally treated, generating microplastics and plastic-char which end up as landfill. This study investigated the potential of plastic-char for treating persistent organic pollutants of aqueous media using 17α-ethinylestradiol (EE2) as a target contaminant. The adsorption and photodegradation capacity of plastic-char were investigated, and the adsorption isotherms revealed that EE2 adsorption on char is heterogeneous and multilayered. The presence of Fe was found to greatly enhance EE2 adsorption rate and capacity as well as photochemical degradation ability of plastic-char. Quenching experiments proved that electron transfer between triplet states of plastic-char and Fe(III) and the production of H₂O₂ were the rate-limited steps in the generation of reactive species. Hydroxyl radical and holes were found to be the predominant reactive species contributing to the EE2 photodegradation. This study not only elucidated the possible environmental behavior of plastic-char discharged as bottom ash in the natural transformation of persistent organic pollutants, but also suggested that water treatment may offer a use for some of the enormous volume of plastic waste now being generated worldwide.