Insight into n-CaO2/SBC/Fe(II) Fenton-like system for glyphosate degradation: pH change, iron conversion, and mechanism

Recent progress in TiO2-biochar-based photocatalysts for water contaminants treatment: strategies to improve photocatalytic performance

Toxic organic pollutants in wastewater have seriously damaged human health and ecosystems. Photocatalytic degradation is a potential and efficient tactic for wastewater treatment. Among the entire carbon family, biochar has been developed for the adsorption of pollutants due to its large specific surface area, porous skeleton structure, and abundant surface functional groups. Hence, combining adsorption and photocatalytic decomposition, TiO2-biochar photocatalysts have received considerable attention and have been extensively studied. Owing to biochar's adsorption, more active sites and strong interactions between contaminants and photocatalysts can be achieved. The synergistic effect of biochar and TiO2 nanomaterials substantially improves the photocatalytic capacity for pollutant degradation. TiO2-biochar composites have numerous attractive properties and advantages, culminating in infinite applications. This review discusses the characteristics and preparation techniques of biochar, presents in situ and ex situ synthesis approaches of TiO2-biochar nanocomposites, explains the benefits of TiO2-biochar-based compounds for photocatalytic degradation, and emphasizes the strategies for enhancing the photocatalytic efficiency of TiO2-biochar-based photocatalysts. Finally, the main difficulties and future advancements of TiO2-biochar-based photocatalysis are highlighted. The review gives an exhaustive overview of recent progress in TiO2-biochar-based photocatalysts for organic contaminants removal and is expected to encourage the development of robust TiO2-biochar-based photocatalysts for sewage remediation and other environmentally friendly uses.

Applying bottom ash as an alternative Fenton catalyst for effective removal of phenol from aqueous environment

In this study, coal bottom ash from a thermoelectric plant was tested as an alternative Fenton catalyst for phenol degradation in water. The effect of operating parameters such as initial pH, catalyst dosage and H2O2 concentration were evaluated. The characterization results indicated that the material has a mesoporous structure, with active species (Fe) well distributed on its surface. Under the optimal reaction conditions (6 mM H2O2, 1 g L-1 of catalyst and pH = 3), 98.7% phenol degradation efficiency was achieved in 60 min, as well as 71.6% TOC removal after 150 min. Hydroxyl radical was identified as the main oxidizing agent involved on the cleavage of the phenol molecule. After four consecutive reuse cycles, phenol degradation efficiency was around 80%, indicating good reusability and stability of the catalyst. Therefore, the obtained results demonstrated that the bottom ash presents remarkable activity for application in the Fenton reaction towards phenol degradation.

Facile and innovative application of surfactant-modified-zeolite from Austrian fly ash for glyphosate removal from water solution

This study highlights a pioneering approach in the development of an efficient, affordable, and economically feasible adsorbent specifically tailored for the removal of glyphosate (Gly) from contaminated water. To accomplish this objective, a low-cost and pure NaA Zeolite (NaAZ) was synthesized with 93% crystallinity from Austrian fly ash (AFA) as a precursor for the first-time. Taguchi design was employed to optimize critical parameters such as the SiO2/Al2O3 ratio, alkalinity concentration, time, and temperature. The cation exchange capacity (CEC) and external cation exchange capacity (ECEC) are determined as critical factors for the modification process. Subsequently, the pure NaAZ was modified with hexadecyl trimethyl ammonium chloride (HDTMAC), a cationic surfactant. The utilization of surfactant-modified zeolite (SMZ) for Gly removal demonstrates its innovative application in this field, highlighting its enhanced adsorption capacity and optimized surface properties. The AFA, NaAZ, and SMZ were characterized using analytical techniques including XRD, XRF, FTIR-ATR, SEM, TGA, BET, CHNSO analyzer and ICP-OES. The adsorbent exhibited effective Gly removal through its pH-dependent charge properties (pH 2-10), with an optimized pH 6 facilitating a significant electrostatic interaction between the adsorbent and Gly. SMZ demonstrated remarkable adsorption capacity and removal efficacy, surpassing most reported adsorbents with values of 769.23 mg/g and 98.92% respectively. Our study demonstrates the significant advantage of the SMZ, with a low leaching concentration of only 6 ppm after 60 days, ensuring environmental safety, long-term stability, and public health considerations. The kinetics of the adsorption process was well described by the pseudo-second order and the Freundlich isotherm. Pore diffusion and H-bonding were postulated to be involved in physisorption, whereas electrophilic interactions led to chemisorption type of adsorption. Consequently, SMZ provides a practical significance, broad applicability and promising solution for Gly removal, facilitating sustainable water treatment.

Feasibility of a Heterogeneous Nanoscale Zero-Valent Iron Fenton-like Process for the Removal of Glyphosate from Water

Glyphosate is a widely used herbicide, and it is an important environmental pollutant that can have adverse effects on human health. Therefore, remediation and reclamation of contaminated streams and aqueous environments polluted by glyphosate is currently a worldwide priority. Here, we show that the heterogeneous nZVI-Fenton process (nZVI + H₂O₂; nZVI: nanoscale zero-valent iron) can achieve the effective removal of glyphosate under different operational conditions. Removal of glyphosate can also take place in the presence of excess nZVI, without H₂O₂, but the high amount of nZVI needed to remove glyphosate from water matrices on its own would make the process very costly. Glyphosate removal via nZVI--Fenton was investigated in the pH range of 3-6, with different H₂O₂ concentrations and nZVI loadings. We observed significant removal of glyphosate at pH values of 3 and 4; however, due to a loss in efficiency of Fenton systems with increasing pH values, glyphosate removal was no longer effective at pH values of 5 or 6. Glyphosate removal also occurred at pH values of 3 and 4 in tap water, despite the occurrence of several potentially interfering inorganic ions. Relatively low reagent costs, a limited increase in water conductivity (mostly due to pH adjustments before and after treatment), and low iron leaching make nZVI-Fenton treatment at pH 4 a promising technique for eliminating glyphosate from environmental aqueous matrices.