Synthesis of X@DRHC (X=Co, Ni, Mn) catalyst from comprehensive utilization of waste rice husk and spent lithium-ion batteries for efficient peroxymonosulfate (PMS) activation

Nitrogen-mediated engineering cobalt phosphide sites for enhanced peroxymonosulfate activation towards organic wastewater purification

Introducing heteroatoms into cobalt phosphide-based materials is expected to enhance their effectiveness in wastewater purification through peroxymonosulfate (PMS) activation by altering the electronic structure and reconfiguring the catalytic sites. In this study, we describe an efficient one-step calcination method for fabricating CoP@NC/NF, wherein simultaneous phosphorization and nitrogen nitridation occur during the calcination process. The CoP@NC/NF/PMS system effectively activates PMS and achieves a tetracycline (TC) removal rate of 92.3 % within 30 min. The calculated rate constant achieves 0.1615 min-1, representing a 1.85-fold increase compared to the CoP@C/NF/PMS system. Furthermore, the CoP@NC/NF/PMS system exhibits remarkable resistance to interference from various inorganic anions and humic acid. Mechanistic examinations reveal that non-radical pathways including 1O2 and electron transfer are the dominant mechanisms in the catalytic system. Additionally, potential catalytic sites for TC removal via PMS activation by CoP@NC/NF include Co2+, Co-Nx, graphitic N, and C=O. Finally, four potential degradation pathways were identified through the analysis of fourteen intermediates from TC decomposition. Toxicity assessments indicate a marked decrease in the toxicity of the degraded solution. Overall, this catalyst, characterized by multiple active sites and enhanced stability, presents a highly effective oxidation system for eliminating antibiotic pollutants from water.

Oxygen clusters anchoring Co ions in hollow tungstic acid spheres to promote the generation of singlet oxygen for New Coccine degradation

In this study, distinctive hollow spheres assembled by interlaced tungstic acid nanosheets (H2WO4) are synthesized through a facile self-template method. Cobalt ions were strongly coordinated with the oxygen cluster in tungstic acid, successfully preparing the Co/H2WO4 composite for use as a peroxymonosulfate (PMS) activator. Owing to the synergistic effect between oxygen clusters and Co active component as well as the interlaced nanosheets-shells with hollow interior in Co/H2WO4, the composite exhibits appealing degradation performance, achieving 100% degradation of New Coccine (NC) in 40 min. The cavities from interconnected nanosheets and hollow interior can not only provide large areas for Co2+ loading, but also assist the significant improvement of reaction contact efficiency during the degradation processes. It was found that non-free radical of singlet oxygen (1O2) is the major reactive oxygen species playing a critical role in high-efficiency degradation of NC, comparing with generated hydroxyl radicals (•OH) and superoxide (O2•-). The Co/H2WO4/PMS system also shows strong resistance to inorganic ions and pH during the degradation. This study offers a new strategy for effectively designing H2WO4 materials with novel morphological structure and provides a reference for designing high-performance catalyst in water treatment.

Green adsorbents for pharmaceutics removal from urine: Analysis of isotherms, kinetics, adsorption interactions, cost estimation, and environmental impact

Husks of rice (RH), coffee (CH), and cholupa (CLH) were used to produce natural adsorbents. The natural adsorbents were used to remove pharmaceuticals such as diclofenac, ciprofloxacin, and acetaminophen in a mixture of distilled water. However, CH stood out for its efficiency in removing ciprofloxacin (74%) due to the higher concentration of acidic groups, as indicated by the Boehm method. In addition, CH removed 86% of ciprofloxacin individually. Therefore, CH was selected and used to remove other fluoroquinolones, such as levofloxacin and Norfloxacin. Although electrostatic interactions favored removals, better removal was observed for ciprofloxacin due to its smaller molecular volume. Then, ciprofloxacin was selected, and the effect of pH, matrix, and adsorbent doses were evaluated. In this way, using a pH of 6.2 in urine with a dose of 1.5 g L-1, it is possible to adsorb CIP concentrations in the range (0.0050-0.42 mmol L-1). Subsequently, the high R2 values and low percentages of APE and Δq indicated better fits for pseudo-second-order kinetics, suggesting a two-stage adsorption. At the same time, the Langmuir isotherm recommends a monolayer adsorption with a Qm of 25.2 mg g-1. In addition, a cost of 0.373 USD/g CIP was estimated for the process, where the material can be reused up to 4 times with a CIP removal in the urine of 51%. Consequently, thermodynamics analysis showed an exothermic and spontaneous process with high disorder. Furthermore, changes in FTIR analysis after adsorption suggest that CH in removing CIP in urine involves electrostatic attractions, hydrogen bonds and π-π interactions. In addition, the life cycle analysis presents, for the 11 categories evaluated, a lower environmental impact of the CIP removal in urine with CH than for the preparation of adsorbent, confirming that the adsorption process is more environmentally friendly than materials synthesis or other alternatives of treatments. Furthermore, future directions of the study based on real applications were proposed.