CuCr2O4@CaFe-LDO photocatalyst for remarkable removal of COD from high-strength olive mill wastewater

Recycling Fe and improving organic pollutant removal via in situ forming magnetic core-shell Fe3O4@CaFe-LDH in Fe(II)-catalyzed oxidative wastewater treatment

Due to its high efficiency, Fe(II)-based catalytic oxidation has been one of the most popular types of technology for treating growing organic pollutants. A lot of chemical Fe sludge along with various refractory pollutants was concomitantly produced, which may cause secondary environmental problems without proper disposal. We here innovatively proposed an effective method of achieving zero Fe sludge, reusing Fe resources (Fe recovery = 100%) and advancing organics removal (final TOC removal > 70%) simultaneously, based on the in situ formation of magnetic Ca-Fe layered double hydroxide (Fe3O4@CaFe-LDH) nano-material. Cations (Ca2+ and Fe3+) concentration (≥ 30 mmol/L) and their molar ratio (Ca:Fe ≥ 1.75) were crucial to the success of the method. Extrinsic nano Fe3O4 was designed to be involved in the Fe(II)-catalytic wastewater treatment process, and was modified by oxidation intermediates/products (especially those with COO- structure), which promoted the co-precipitation of Ca2+ (originated from Ca(OH)2 added after oxidation process) and by-produced Fe3+ cations on its surface to in situ generate core-shell Fe3O4@CaFe-LDH. The oxidation products were further removed during Fe3O4@CaFe-LDH material formation via intercalation and adsorption. This method was applicable to many kinds of organic wastewater, such as bisphenol A, methyl orange, humics, and biogas slurry. The prepared magnetic and hierarchical CaFe-LDH nanocomposite material showed comparable application performance to the recently reported CaFe-LDHs. This work provides a new strategy for efficiently enhancing the efficiency and economy of Fe(II)-catalyzed oxidative wastewater treatment by producing high value-added LDHs materials.

Bismuth-based nanostructured photocatalysts for the remediation of antibiotics and organic dyes

A serious threat to human health and the environment worldwide, in addition to the global energy crisis, is the increasing water pollution caused by micropollutants such as antibiotics and persistent organic dyes. Nanostructured semiconductors in advanced oxidation processes using photocatalysis have recently attracted a lot of interest as a promising green and sustainable wastewater treatment method for a cleaner environment. Due to their narrow bandgaps, distinctive layered structures, plasmonic, piezoelectric and ferroelectric properties, and desirable physicochemical features, bismuth-based nanostructure photocatalysts have emerged as one of the most prominent study topics compared to the commonly used semiconductors (TiO₂ and ZnO). In this review, the most recent developments in the use of photocatalysts based on bismuth (e.g., BiFeO₃, Bi₂MoO₆, BiVO₄, Bi₂WO₆, Bi₂S₃) to remove dyes and antibiotics from wastewater are thoroughly covered. The creation of Z-schemes, Schottky junctions, and heterojunctions, as well as morphological modifications, doping, and other processes are highlighted regarding the fabrication of bismuth-based photocatalysts with improved photocatalytic capabilities. A discussion of general photocatalytic mechanisms is included, along with potential antibiotic and dye degradation pathways in wastewater. Finally, areas that require additional study and attention regarding the usage of photocatalysts based on bismuth for removing pharmaceuticals and textile dyes from wastewater, particularly for real-world applications, are addressed.

Sheep Dung Ash as a Low-Cost Adsorbent for the Reduction of COD of Highly Polluted Oilfield-Produced Water

Herein, we introduce a low-cost, available, renewable, and effective solid adsorbent used for oilfield-produced-water treatment using a straightforward treatment process. In the present study, sheep dung ash was prepared using the same way this waste is produced in rural areas when sheep dung is used as a source of energy for cooking and heating: by burning sheep dung with a direct flame. The prepared ash was characterized using FTIR, EDX, and SEM analysis techniques. The feasibility of the ash as a low-cost, available, renewable, and effective adsorbent for reducing the COD of oilfield-produced water with the initial COD of 21,600 mg/L was investigated. The effect of adsorbent dose, contact time (in hours and days), initial pH value, and initial COD value on the efficiency of sheep dung ash in COD adsorption was examined at room temperature. With shaking, the maximum capacity of sheep dung ash for COD reduction was found to be 71.8% at an adsorbent dosage of 30 g/L, an initial pH of 7, and a contact time of 1 h. Without shaking, a maximum capacity of 75% for COD reduction was obtained at an adsorbent dosage of 30 g/L, an initial pH of 7, and a contact time of 4 days. By applying the experimental results on Langmuir and Freundlich models of adsorption, it was found that the adsorption process of COD causing molecules follows both Langmuir and Freundlich models.