The possibility of Pb²⁺, Cd²⁺, Ni²⁺ and Ba²⁺ ions removal from aqueous solution using light expanded clay aggregate (LECA) was investigated in this work. The central composite design (CCD) in response surface methodology (RSM) was used to optimize the operating parameters (adsorbent granulometry, absorption time and initial metal ions concentration) to reach the maximum ions removal in single and multi-elemental solutions. After optimization, the results shows that the removal efficiency decrease following the ion sequence Pb²⁺ > Ba²⁺ > Cd²⁺ > Ni²⁺ ions. The better efficiency (~95%) is observed for the Pb²⁺. The Langmuir and Freundlich isotherm models were applied to the equilibrium data at room temperature. The results revealed that data on LECA was very well fitted with Langmuir equations. The real interest of this work is to demonstrate that a simple material such as LECA can be used to remove extremely small levels of toxic metals, such as those found in drinking water. So our results could be the starting point for the development of a low-cost filtration system to remove toxic metals.

Humic substances (HSs) pose a significant challenge to safe drinking-water production due to their ubiquity, limited removal by conventional methods, and their role in forming toxic disinfection by-products, reinforcing the need for more efficient, energy-favorable, and scalable treatment technologies. This study developed and evaluated a compact hydrodynamic cavitation (HC) system that simultaneously induces coagulation and generates microbubbles for flotation-based HS removal. For the first time, HC is explored as a multifunctional unit capable of integrating rapid mixing, coagulant destabilization, and flotation within a single device. Optimal coagulation conditions were established at pH 5.0 and 9.5 mg L⁻¹ of ferric chloride. Process optimization using a Rotated Central Composite Design demonstrated that inlet pressure, flotation time, and initial HS concentration were the dominant operational factors, enabling the HC system to achieve a maximum removal efficiency of 81.9%. Five Venturi geometries with divergent angles of 4°, 8°, 11°, 14°, and 90° were investigated, with the 8° Venturi exhibiting superior performance due to stable microbubble formation and effective coagulant dispersion, as confirmed by CFD analyses. Comparative tests with a conventional Flotest unit showed that achieving similar efficiencies required at least 30% saturated water. In contrast, the HC system delivered equivalent removal in continuous flow without external air saturation. These findings demonstrate the potential of HC as an integrated coagulation–flotation core and highlight its promise as a compact, energy-efficient, and scalable technology for natural organic matter removal in water treatment.