Efficient removal of uranium(VI) from aqueous solution by a novel phosphate-modified biochar supporting zero-valent iron composite

Nonmetallic modified zero-valent iron for remediating halogenated organic compounds and heavy metals: A comprehensive review

Zero Valent Iron (ZVI), an ideal reductant treating persistent pollutants, is hampered by issues like corrosion, passivation, and suboptimal utilization. Recent advancements in nonmetallic modified ZVI (NM-ZVI) show promising potential in circumventing these challenges by modifying ZVI's surface and internal physicochemical properties. Despite its promise, a thorough synthesis of research advancements in this domain remains elusive. Here we review the innovative methodologies, regulatory principles, and reduction-centric mechanisms underpinning NM-ZVI's effectiveness against two prevalent persistent pollutants: halogenated organic compounds and heavy metals. We start by evaluating different nonmetallic modification techniques, such as liquid-phase reduction, mechanical ball milling, and pyrolysis, and their respective advantages. The discussion progresses towards a critical analysis of current strategies and mechanisms used for NM-ZVI to enhance its reactivity, electron selectivity, and electron utilization efficiency. This is achieved by optimizing the elemental compositions, content ratios, lattice constants, hydrophobicity, and conductivity. Furthermore, we propose novel approaches for augmenting NM-ZVI's capability to address complex pollution challenges. This review highlights NM-ZVI's potential as an alternative to remediate water environments contaminated with halogenated organic compounds or heavy metals, contributing to the broader discourse on green remediation technologies.

A Dual-Signal Sensing for the Visual and Luminescent Detection of p-Phenylenediamine Based on Cerium-Nitrogen-Co-Doped Carbon Dots

Herein, a visual and luminescent dual-mode (colorimetric and fluorometric) method for the detection of P-phenylenediamine (PPD) in hair dye was successfully established based on cerium-nitrogen co-doped carbon dots (Ce, N-CDs) that displayed remarkable luminescence and peroxidase activity. Ce, N-CDs catalyzed H2O2 to produce superoxide anion, which then oxidized the colorless 3,3,5,5-tetramethylbenzidine (TMB) into blue oxidized TMB (oxTMB), capable of quenching the fluorescence through fluorescence resonance energy transfer (FRET) between Ce, N-CDs and oxTMB. The reducing properties of PPD could reduce oxTMB back to TMB, leading to a decrease in the absorption intensity of oxTMB and a fluorescence recovery of Ce, N-CDs. As a result, the quantitative detection of PPD could be achieved by measuring the absorption values of oxTMB and the fluorescence signal of Ce, N-CDs. The detection limits for PPD were calculated as 0.36 µM and 0.10 µM for colorimetry and fluorimetry, respectively. Furthermore, smartphone application (ColorPicker) capable of measuring the RGB value of the color was utilized in the detection system, facilitating on-site quantitative detection. This approach effectively shortens the detection time and simplifies the operation, offering a powerful and convenient tool for real-time monitoring of PPD.

Colorimetric sensing for the sensitive detection of UO22+via the phosphorylation functionalized mesoporous silica-based controlled release system

In this study, we developed a simple and sensitive colorimetric sensing method for the detection of UO22+, which was built to release MB from the molybdenum disulfide with a phosphate group (MoS2-PO4) gated mesoporous silica nanoparticles functionalized phosphate group (MSN-PO4) with UO22+ chelating. In the presence of UO22+, MoS2-PO4 can be effectively adsorbed onto the surface of MSN-PO4 based on the coordination chemistry for strong affinity between the P-O bond and UO22+. The adsorbed MoS2-PO4 was then utilized as an ideal gate material to control the release of signal molecules (MB) entrapped within the pores of MSN-PO4, resulting in a detectable decrease in the absorption peak at 663 nm. This colorimetric sensing demonstrated the advantages of simplicity and easy manipulation and exhibited a linear response to the concentration of UO22+ within the range of 0.02-0.2 μM. The detection limit of UO22+ was determined to be 0.85 nM, which was lower than the limit (130 nmol L-1) set by the US Environmental Protection Agency. Furthermore, the proposed colorimetric sensing method has been utilized to determine UO22+ in samples of Xiangjiang River and tap water, and a high recovery rate was achieved. This method shows promising potential in preventing and controlling environmental pollution.

Waterborne Diseases and Wastewater Treatment in Iraq

Iraq is a desert country with access to large river resources and an extensive aquifer, but these have already been overdrawn for domestic, industry and agriculture use. The diminished flow of the Tigris and Euphrates rivers has allowed seawater intrusion from the Persian Gulf 110 km up as far as Basra, the county's third largest city. In addition, water distribution systems are overloaded and wastewater treatment plants (WWTPs) need upgrading, and fresh water sources polluted by lack of sanitation, agricultural runoff, household and industrial waste, and including the irrigation of vegetables with sewage water, have led to episodes of bacterial, viral and parasitic diseases. Also, there have been increases in many types of cancer since the early 1990s, and based on clinical and epidemiological data, these increases could be attributable to exposure to depleted uranium in the environment arising from conflict in Iraq and particularly during the Iraqi War started 20 years ago. The population affected would like government action to reduce their health concerns, and policies that have been proposed for improving water availability and quality, as well as but have not been followed up sufficiently to tackle these, including increasing the capacity and efficiency of WWTP; promoting the most efficient irrigation techniques for the local growing conditions; reducing the use of chemical fertilizers and pesticides that can decrease the water quality; reducing saline intrusion challenges; building compact desalination units; constructing water storage facilities to address water scarcity challenges; and establishing public education plans for consumers to reduce the water demand during the hot season. Whether the government rises to the task remains to be seen. Also, do those countries that used the DU have a responsibility to remove or otherwise dispose of the fragments that remain?