Arsenic contamination in water remains a critical global challenge, particularly in rural and resource-limited regions. Clays have been widely studied as cost-effective and efficient adsorbents for arsenic removal. This systematic review provides a comprehensive analysis of the application of clays in arsenic adsorption, focusing on clay types, operational units, and study methodologies. The review classifies the adsorption mechanisms, highlights key factors influencing adsorption performance—such as pH, ionic strength, and surface modifications—and examines the effectiveness of various modifications. Furthermore, the study categorizes adsorption research into kinetic, iso-thermal, thermodynamic, and efficiency studies, providing insights into the state of the art and the experimental conditions that govern arsenic removal. It also discusses the scalability and practical application of clay-based adsorption technologies, emphasizing gaps in field validation, regeneration studies, and large-scale implementation. The findings highlight the potential of natural and modified clays in arsenic remediation, while underscoring the need for further research to optimize adsorption conditions and enhance sustainability in water treatment systems.

Natural gas remains an important global source of energy. Usually, sour gas from the well or refinery stream contains H₂S among other contaminants that should be removed to fulfill permissible standards of use. Despite the use of different gas-liquid sour gas upgrading technologies, ionic liquids (ILs) have been recognized as promising materials to remove H₂S from sour gas. However, data concerned with thermodynamic solution functions of H₂S in ILs have scarcely been reported in the literature. In this work, solution ¹H NMR spectroscopy was employed for quantifying H₂S soluble in [BMIM][Cl] and for gaining a better understanding of the H₂S-IL interaction. Experiments were carried out in a Young-Tap NMR tube containing a saturated solution of H₂S/CH₄/[BMIM][Cl] and recording spectra from 298 to 333 K. The thermodynamic solution functions, determined from the Van't Hoff equation, showed that solubility of the H₂S in the [BMIM][Cl] is an exothermic gas-liquid physisorption process (Δ_solH° = -66.13 kJmol^-1) with a negative entropy change (Δ_solS° = -168.19 JK^-1 mol^-1). ¹H NMR spectra of the H₂S/[BMIM][Cl] solution show a feature of strong solute-solvent interactions. However, solubility enthalpy is a fifth of the H-S bond energy value. Results from ¹H NMR spectroscopy also agree with those from the bench dynamic experiments.