Regarding the long-term toxic effects of Pb (II) ions on human health and its bioaccumulation property, taking measures for its reduction in the environment is necessary. The MMT-K₁₀ (montmorillonite-k₁₀) nanoclay was characterized by XRD, XRF, BET, FESEM, and FTIR. The effects of pH, initial concentrations, reaction time, and adsorbent dosage were studied. The experimental design study was carried out with RSM-BBD method. Results prediction and optimization were investigated with RSM and artificial neural network (ANN)-genetic algorithm (GA) respectively. The RSM results showed that the experimental data followed the quadratic model with the highest regression coefficient value (R² = 0.9903) and insignificant lack of fit (0.2426) showing the validity of the Quadratic model. The optimal adsorption conditions were obtained at pH 5.44, adsorbent = 0.98 g/l, concentration of Pb (II) ions = 25 mg/L, and reaction time = 68 min. Similar optimization results were observed by RSM and artificial neural network-genetic algorithm methods. The experimental data revealed that the process followed the Langmuir isotherm and the maximum adsorption capacity was 40.86 mg/g. Besides, the kinetic data indicated that the results fitted with the pseudo-second-order model. Hence, the MMT-K₁₀ nanoclay can be a suitable adsorbent due to having a natural source, simple and inexpensive preparation, and high adsorption capacity.

The CS-TPP nanoparticles were synthesized and their efficiency for removal of arsenic (V) ions at the optimum conditions was investigated. The optimum conditions for CS-TPP nanoparticles were obtained with the mass ratio of tripolyphosphate to chitosan of 1: 2 and pH = 5.0. The experimental data for the adsorption of As (V) ions followed the Freundlich adsorption isotherm and the maximum adsorption capacity was 77 mg/g at pH = 6.0. All isotherm experiments were performed at room temperature (25 °C). The crosslinking of sodium tripolyphosphate with the chitosan led to a decrease in crystallinity of the formed particles which then resulted in an improvement in metal ion sorption properties.

Magnetic bentonite (MBt) and Ti/TiO2 nanotube/PbO2, for the first time, were investigated as particle electrodes and anode of three dimensional electro-Fenton process (3DEF) for the degradation of diclofenac (DCF) and naproxen (NPX). The characteristics of the electrodes were determined by X-ray diffraction(XRD), scanning electron microscope(SEM) and energydispersive X-ray spectroscopy(EDS) analyses and the effects of operating parameters on degradation were studied. The results showed that adsorption and electrochemical processes have lower removal efficiency than the 3DEF process at neutral pH. This efficiency was due to the greater production of hydroxyl radical (•OH) through the anode and MBt surface. The results of the scavenging experiments confirmed an increase in the amount of production of •OH. The maximum removal efficiency of DCF and NPX was obtained at pH of 6, MBt dosage of 500 mg/L, current density of 25 mA/cm²and electrolysis time of 120 min. The electrodes reusability was confirmed by consecutive reaction cycle and the Fourier-transform infrared spectroscopy (FTIR) and SEM-mapping analysis explained their stability. The results of continuous electro-oxidation reactor showed proper removal of the chemical oxygen demand(COD) from real wastewater. The degradation by-products were identified by gas chromatography mass-spectrometry (GC-MS) analysis coupled with dispersive liquid–liquid microextraction (DLLME). Based on comparative tests and products identification, the possible mechanism and pathway of drugs degradation were suggested.