Search

Abstract: The toxicity of mercury (Hg) to humans, including damage to the nervous system, is well known. Hg cannot be degraded into non-toxic compounds or other elements. It is released mainly through mining, industries, and fossil fuel combustion. Anthropogenic and natural activities, such as volcanoes, transform elemental Hg (Hg0) into its ionic form [Hg(II)], which bioaccumulates in biota and is biomagnified in the food chain, notably in aquatic environments. This critical report aims to control Hg(II)-ion toxicity through risk assessment, recognition, and removal via high-level waste management. We first discuss successful and up-to-date developments in different techniques, designs and studies that are potentially useful in enhancing the effectiveness of control of Hg(II)-ion toxicity. The key to designing optical nanosensors is to construct chromophore and fluorophore receptors as nanoscale platform scavengers with different functional characteristics (e.g., density, accessibility, and intrinsic mobility), which allow for easy, reliable signaling in continuous monitoring modes. We highlight a technique that depends on the use of engineered mesocage materials that have multidirectional cavities and microsized, particle-like monoliths to control the adsorption/detection of toxic metal ions, especially Hg(II) ions. With regard to proximal sensing, we consider controlled assessment processes that involve the evaluation of intrinsic properties (e.g., signal change, long-term stability, adsorption efficiency, extraordinary sensitivity, selectivity, and reusability). This study provides evidence that miniaturized mesosensor strips can revolutionize consumer and industrial markets with the introduction of ion-sensor strips. [Copyright &y& Elsevier]

The complete remediation of extremely toxic elements, such as cadmium, must be achieved to control the various stages in their life cycles, from mining as virgin ore to using them as consumer and industrial end products, and recycling. Considerable progress has been made in monitoring cadmium ions, but sensors or captors that can simultaneously detect and remove toxic metal ions across a wide range of environments are still greatly needed. This article reviews the tools and the strategies for the environmental remediation of cadmium ions, with special emphasis on state-of-the-art colorimetric sensors. Selective colorimetric sensors based on immobilization of hydrophobic or hydrophilic chromophore molecules into nanosized space cavities have significant advantages because of their dual functionality, namely, early warning “detection” and removal of cadmium ions. This review concludes with a thorough evaluation of emerging challenges and future requirements in monitoring, detecting, and removing cadmium ions from environmental matrices. [ABSTRACT FROM AUTHOR]

Alkali treated tea waste (ATTW) was investigated as a novel alternative cost-effective natural adsorbent to decontaminate the pollutant of chromium (Cr(VI)) in the polluted water with the variation of equilibration time, solution pH, initial Cr(VI) concentration, adsorbent dosage, and temperature with a view to ensuring a safe disposal as well as sustainable management of the discarded bulk quantities of industrial tea leaves wastes. The adsorbent characteristic was confirmed the significant amount of Cr(VI) accumulation onto ATTW surfaces. The adsorption processes were satisfactorily described by pseudo-first order (PFO), pseudo-second order (PSO) and intra-particles diffusion models (IDM) where the PSO model evidently shows a better fitting with the regression coefficient (R 2 = 0.994). Exploration of Langmuir, Freundlich, Flory-Huggins, and Temkin isotherm models were also investigated and the best fitting was observed for the Langmuir model as it was produced the highest regression coefficient value (R 2 = 0.993). The maximum adsorption ability of ATTW according to the Langmuir model was found to be 158.73 mg/g. These results demonstrate that Cr(VI) adsorption was a complex process involving a physicochemical spontaneous monolayer and multiple rate-limiting states, which was predominantly chemical or chemisorption due to ion-exchange or electrostatic attraction/surface complexation formation, film diffusion and intra-particle diffusion. Furthermore, the substrates exhibited an excellent regeneration capacity upon using 0.10 M HNO 3 as eluent and ATTW was reused several cycles without influencing the adsorption performance. The results of this study thus concludes that ATTW could be a promising environmentally friendly and cheap bio-adsorbent for Cr(VI) remediation with profound implications in water and wastewater treatment for a large-scale environmental pollutant clean-up laden with toxic Cr(VI) ions. Unlabelled Image • A natural adsorbent was developed using alkali treated tea waste for pollutant removal. • The developed adsorbent demonstrated high adsorption to clean up wastewater efficiently. • The pollutant removal was predominantly governed by the chemisorption mechanisms. [ABSTRACT FROM AUTHOR]