Pd–Ni nanoparticles supported on activated carbon (Pd–Ni/AC) were prepared using a phase transfer method. The purpose of synthesizing ternary composites was to enhance the surface area of synthesized Pd–Ni nanoparticles, as they have a low surface area. The resulting composite was characterized by scanning electronic microscopy (SEM), X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX) for investigating its surface morphology, particle size, percentage of crystallinity and elemental composition, respectively. The XRD data and EDX analysis revealed the presence of Pd–Ni alloys impregnated on the AC. Pd–Ni/AC was used as an adsorbent for the removal of the azo dye basic blue 3 from an aqueous medium. Kinetic and isotherm models were used to calculate the adsorption parameters. The most suitable kinetic model amongst the applied models was the pseudo-second-order model, confirming the chemisorption characteristics of the process, and the most suitable isotherm model was the Langmuir model, with a maximum adsorption capacity of 333 mg/g at 333 K. Different experimental parameters, such as the adsorbent dosage, pH, temperature and contact time, were optimized. The optimum parameters reached were: a pH of 12, temperature of 333 K, adsorbent dosage of 0.01 g and optimum contact time of 30 min. Moreover, the thermodynamics parameters of adsorption, such as Gibbs free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°), showed the adsorption processes being exothermic with values of ΔH° equal to −6.206 kJ/mol and being spontaneous with ΔG° values of −13.297, −13.780 and −14.264 kJ/mol, respectively at 293, 313 and 333 K. An increase in entropy change (ΔS°) with a value of 0.0242 kJ/mol K, indicated the enhanced disorder at a solid–solution interface during the adsorption process. Recycling the adsorbent for six cycles with sodium hydroxide and ethanol showed a decline in the efficiency of the selected azo dye basic blue 3 up to 79%. The prepared ternary composite was found effective in the removal of the selected dye. The removal of other pollutants represents one of the possible future uses of the prepared adsorbent, but further experiments are required.

In this study, Ailanthus altissima sawdust was chemically activated and characterized by Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FTIR), Energy Dispersive X rays (EDX), and surface area analyzer. The sawdust was used as an adsorbent for the removal of azo dye; Acid Yellow 29 (AY 29) from wastewater. Different kinetic and equilibrium models were used to calculate the adsorption parameters. Among the applied models, the more suitable model was Freundlich with maximum adsorption capacities of 9.464, 12.798, and 11.46 mg/g at 20 °C, 30 °C, and 40 °C respectively while R² values close to 1. Moreover, the kinetic data was best fitted in pseudo second order kinetic model with high R² values approaching to 1. Furthermore, adsorption thermodynamics parameters such as free energy, enthalpy, and entropy were calculated and the adsorption process was found to be exothermic with a value of ∆H° = −9.981 KJ mol⁻¹, spontaneous that was concluded from ΔG° values which were negative (−0.275, −3.422, and −6.171 KJ mol⁻¹ at 20, 30, and 40 °C respectively). A positive entropy change ∆S° with a value of 0.0363 KJ mol⁻¹ indicated the increase disorder during adsorption process. It was concluded that the activated sawdust could be used as a suitable adsorbent for the removal of waste material, especially dyes from polluted waters.

The Silica monolith particles (SMP) were prepared from Tetra-Methyl-Ortho-Silicate (TMOS) and characterized by Fourier transforms infrared (FTIR), Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and surface area analyzer. FTIR analysis showed the Si−O stretching confirming SMP formation. SEM analysis provided information about the mean diameter of SMP (1−5 µm). EDX confirmed the presence of silicon and oxygen in the SMP. Moreover, the calculated surface area for SMP was found to be around 367 m²/g, whereas BJH pore size distributed particles were 87.15 along with the total pore volume and pore radius of 0.073 cm³/g and 16.627 Å, respectively. Besides, the removal efficiency was found to be about 96%. Various kinetic equations were used to calculate the adsorption parameters. Overall, the results show that the most appropriate model for the kinetics data was the pseudo-second order kinetics model while the mechanism of adsorption was best explained by the Langmuir isotherm. The highest removal of Basic Red 5 dye after 120 min at 298 K was 576 mg/g. Moreover, the thermodynamics parameters (Enthalpy, Gibb’s energy, and Entropy) were also estimated. The ΔH° (0.995 kJ/mol) value depicted the endothermic nature of the process. The non-spontaneous aspect of the process was evident from the ΔG° values which were 60.431, 328.93, and 339.5 kJ/mol at 293, 303, and 313 K, respectively. From the high removal efficiency value, it can be concluded that the prepared adsorbent can be a potential adsorbent in the reclamation of dyes from wastewater.

The removal of water pollutants by photocatalysis is a promising technique, mainly due to its environmentally friendly and sustainable nature. In this study, the degradation of a recalcitrant organic pollutant, malachite green (MG), was investigated in water by a microstructured silver oxide photocatalyst. The silver oxide (Ag₂O) microparticles (MPs) were synthesized by a low-cost, green method, mediated by green tea leaves extract. The surface, morphological and optical properties of the synthesized Ag₂O MPs were determined by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD) analysis, Fourier transform infrared (FTIR) spectroscopy, and ultraviolet-visible (UV-visible) spectrophotometry. The synthesized Ag₂O MPs showed good photoactivity, represented by 83% degradation of malachite green (MG) ([C]₀ = 0.4 mM, Ag₂O loading = 0.1 g L⁻¹) at neutral pH, in 3 h. Persulfate ions (PS) showed a strong synergistic effect on the efficiency of solar/Ag₂O photocatalysis, represented by complete MG removal in 15 min, in the presence of 1.6 mM PS. The results revealed that solar/Ag₂O, particularly solar/Ag₂O/PS photocatalysis is a promising method for the elimination of toxic organic pollutants, such as malachite green, from the water environment.

In the present study, we determined the levels of chlorinated pesticide residues in surface water samples collected from the Charsadda district (KPK, Pakistan). SPME-GC-ECD with COMBI PAL CTC autosampler was used for extraction and analysis of 20 organochlorine pesticides in the collected water samples. For maximum efficiency of the SPME procedure, several parameters were studied, including the extraction and desorption time of the fiber, solution pH, agitation of samples, and stirring speed, etc. This method showed good liner response, with R² values in the range of 0.9887 to 0.9999 for all pesticides. This method also provided good percent recoveries at 1 µg L⁻¹ (87.5 to 106.0%) and at 2 µg L⁻¹ (88.5 to 109.2%). Lower limits of detection for all 20 chlorinated pesticides were found to be lower than their maximum permissible contamination levels. Approximately 50% of the surface water samples collected from the Charsadda district were found to be contaminated with the pesticides γ-BHC, heptachlor, aldrin and dieldrin, with maximum concentrations of 0.023, 0.108, 0.014 and 0.013 µg L⁻¹, respectively. For adults and children, the cancer risk from water due to contamination by various pesticides ranged from 0 to 33.29 × 10⁻⁶. The non-carcinogenic risk from each pollutant in the water samples of the Charsadda district was found to be in the order of heptachlor > aldrin > dieldrin > γ-BHC. However, the pesticides α-BHC, β-BHC, heptachlor epoxide, chlordane, endrin, 4,4′-DDD, endrin ketone, 4,4′-DDT, endosulfan sulfate and methoxychlor were not detected in any of the surface water samples of investigated in the present study.