Background: Conserving water for human survival and providing future security are important issues that need to be addressed.
Methods: In this study, a zeolite modified with hexadecyl trimethyl ammonium bromide (HDTMA-Br), a cationic surfactant, and its application in removing direct blue 129 (DB129) was examined. Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) were used to characterize both modified and unmodified zeolites. The effects of operational parameters such as the amount of adsorbent, initial dye concentration and pH on the removal efficiency of the dye were examined.
Results: The results showed that in the initial dye concentration of 50 mg/L, the optimum amounts of adsorbent and pH were 0.3 g and 7, respectively. Increasing the dye concentration from 20 to 100 mg/L resulted in the reduction of the removal efficiency from 100% to 79% in the contact time of 90 minutes. The results indicated the highest attracting correlation with Langmuir model. The maximum adsorbent capacity obtained from Langmuir model was 25 mg/g. The kinetics of the dye adsorption on the modified zeolite followed pseudo-second-order kinetics model. Calculated thermodynamic parameters showed that Gibbs free energy changes (DGo) at temperatures of 20 and 45°C were -29.41 and -35.20 kJ/mol, respectively.
Enthalpy (DHo) and entropy changes were equal to 41.181 kJ/mol and 0.241 J/mol K, respectively. The results showed that the processing was a spontaneous endothermic reaction. The process modeled by artificial neural networks (ANN) showed that the experimental results can be accurately modeled using neural network model. The correlation coefficient found between the experimental and the model results was 0.951.
Conclusion: Due to the low cost, high abundance and availability of zeolite, the removal efficiency of this adsorbent can be increased to desirable levels by modifying.

Background: Metoprolol (MTP) with its low biodegradability is one of the most dominant micropollutant in the effluent of wastewater treatment plants. The aim of this study was to investigate the removal of metoprolol from aqueous solutions by the activated carbon prepared from pine cones.
Methods: The pine cones were activated using thermal activation method. Characteristics of the adsorbent were determined using Brunauer-Emmett-Teller (BET) and scanning electron microscopy (SEM). In this study, the influent of different parameters such as pH, contact time, initial concentrations of metoprolol, adsorbent dose, temperature, adsorption isotherms, and kinetics were investigated.
Results: The maximum removal efficiency of MTP (89.2%) was obtained at pH=8.5, adsorbent dose=1.5 g, contact time=60 min, and initial concentration=50 mg/L. By increasing the adsorbent dose, the removal efficiency also increased, but the adsorption capacity decreased, however, by increasing the initial concentration, the removal efficiency decreased, but the adsorption capacity increased. The isotherm experimental data for metoprolol was best fitted using the Langmuir model, and kinetic data were better described by pseudo-second-order kinetic model. The thermodynamic study indicated that the adsorption of MTP by the adsorbent was feasible, spontaneous, and endothermic.
Conclusion: MTP removal by the activated carbon prepared from pine cones showed that this natural adsorbent is appropriate for removal of metoprolol from aqueous solutions regarding cost, efficiency, and production method.

Background: Today, due to increasing usage of dyes in various industrials and their destructive effects on health and environment, it is necessary to remove them from industrial wastes. Although there are few studies on the use of rice bran modified with polyaniline (RB/PANI) for removal of different dyes, but the effect of this adsorbent on the removal of Acid Orange 7 (AO7) dye has not been evaluated yet. Therefore, this study was conducted to investigate the removal of AO7 dye by RB/PANI as an adsorbent.
Methods: The adsorbent characteristics were determined using scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy. Also, the adsorbent surface area was measured by Brunauer–Emmett–Teller (BET) technique. The method of one-factor-at-a-time was used to optimize various factors including pH, temperature, and adsorbent dosage.
Results: The optimal values for the factors affecting AO7 dye removal were calculated. It was revealed that the maximum dye removal was obtained at pH = 3, temperature = 25˚C, dye concentration = 30 mg/L, adsorbent dosage = 30 mg/L, and contact time= 60 minutes. The maximum removal percentage for RB/PANI was 97.13%. It was also revealed that Langmuir isotherm is the best fitted isotherm model.
Conclusion: According to the results, the polyaniline-modified rice bran could be used as an excellent adsorbent for the removal of AO7 from aqueous solutions. The maximum dye removal efficiency for AO7 was obtained at pH = 3. Also, it was revealed that AO7 dye removal follows the pseudo second order kinetic model and it is a spontaneous process.

Background: Congo red (CR), a harmful dye present in water, requires effective removal methods. This study investigated the utilization of dry green pea husk (DGPH) and its charcoal (CGPH) as economical and eco-friendly adsorbents.
Methods: Various factors, including contact time, pH, adsorbent dosage, initial concentration, and temperature, were investigated to assess their impact on the adsorption process. Also, different models (isotherms, kinetics, and thermodynamics) were compared to describe the adsorption phenomenon.
Results: Equilibrium adsorption was achieved within 30 minutes for both adsorbents. The optimum pH for CR removal was determined to be 2. The adsorption capacity decreased by increasing the adsorbent dosage, whereas it increased by increasing the initial dye concentration. The Langmuir isotherm model demonstrated the best fit for DGPH, while the Freundlich model exhibited the best fit for CGPH. The pseudo-second-order model displayed a superior fit for both adsorbents. To assess the spontaneity and feasibility of the adsorption process, thermodynamic parameters including enthalpy, entropy, and Gibbs free energy were computed. The results indicated that the adsorption of CR on DGPH was endothermic and favorable at lower temperatures, whereas the adsorption on CGPH was exothermic and favorable at higher temperatures. The negative values of Gibbs free energy for the CGPH adsorbent confirmed the spontaneous nature of the adsorption process.
Conclusion: The study establishes that green pea husk and its charcoal are effective and environmentally friendly alternatives for the removal of CR from water.