Mohsen Heidari

Preparation, characterization and Cr(VI) adsorption evaluation of NaOH-activated carbon produced from Date Press Cake; an agro-industrial waste

Date Press Cake (DPC) is an inevitable by-product of date processing industries and may pose environmental problems if not managed properly. In this study, DPC was converted into activated carbon using solid NaOH under various activation conditions. The prepared activated carbon showed high specific surface area (2025.9 m2 g-1) and microporous texture (86.01%). It was successfully applied for the adsorption of Cr(VI) from aqueous solutions with maximum monolayer adsorption capacities as high as 282.8 mg g-1 (pH = 2) and 198.0 mg g-1 (pH = 5). The kinetic and isotherm experimental data of Cr(VI) adsorption onto the activated carbon were best described by Elovich and Redlich-Peterson models, respectively. It was found that the Cr(VI) adsorption onto the DPC-derived activated carbon was predominantly a chemisorption process with limited desorption rates (below 50%). Overall, Date Press Cake could be considered as an abundant and renewable agro-industrial precursor for the production of high quality activated carbon.

Application of ZnO and TiO2 nanoparticles coated onto montmorillonite in the presence of H2O2 for efficient removal of cephalexin from aqueous solutions

This study considers the feasibility of uptake of cephalexin, an emerging contaminant, from aqueous solutions by using green local montmorillonite (GLM), montmorillonite coated with ZnO (ZnO/GLM) and montmorillonite coated with TiO2 (TiO2/GLM) in the presence of H2O2. Batch adsorption experiments were carried out as a function of pH, initial concentration of the cephalexin, adsorbent dosage, contact time, and temperature. Finally, the adsorbents were characterized by XRD, SEM and FTIR analyses. XRD patterns showed dramatic changes in the adsorbents after loading with the nanoparticles, confirming successful placing of the nanoparticles onto GLM. The GLM mineral surface after nanoparticle loading appears to be fully exposed and more porous with irregular shapes in particles diameters of 1-50 microns. FTIR analyses also confirmed dramatic changes in surface functional groups after modification with these nanoparticles. The results showed that the removal efficiency of cephalexin was better at lower pH values. Totally, the removal efficiency increased with increase in adsorbent dosage and contact time and decreased with concentration and temperature increase. The thermodynamics values of ΔGo and ΔHo revealed that the adsorption process was spontaneous and exothermic. In isotherm study, the maximum adsorption capacities (qm) were obtained to be 7.82, 17.09 and 49.26 mg/g for GLM, ZnO/GLM and TiO2/GLM, respectively. Temkin constant (BT) showed that adsorption of cephalexin from solution was exothermic for all three adsorbents.

Wastewater treatment for Amoxicillin removal using magnetic adsorbent synthesized by ultrasound process

In this study, the effect of magnetic adsorbent prepared from Olive kernel (MA-OK) was studied in the Amoxicillin (AMX) removal. The synthesized adsorbent, under a sonochemical method, were characterized using Field emission scanning electron microscope (FESEM), Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) and X-ray diffraction (XRD). The absorption functions in the batch experiments were studied using the expected parameters for the maximum absorption capacities (qm) such as pH, contact time, the dosage adsorbent, and the initial concentration of AMX. The residual amount of AMX were recorded after injection into the HPLC. The proportion of the mobile phase was methanol to water (40:60) at a flow rate of 1 ml/min. Adsorption experimental results indicated that the removal efficiency reaches its maximum using 0.5 g/L of the adsorbent, concentration of AMX (200 mg/L) at contact time of 90 min and pH of 6. The kinetics of the reaction and the adsorption isotherm could be well described by the pseudo-second order equation and the Langmuir adsorption isotherm with a regression coefficient of 0.9981 and 0.9979, respectively. The maximum adsorption capacity obtained from the Langmuir model was to be 238.1 mg/g. The ionic strength of the solution has no significant effect on increasing the AMX removal efficiency. Eventually, application of this adsorbent was successfully performed for removing AMX from aqueous and hospital wastewater solutions.

Removal of bromide from aqueous solutions using the UV/ZnOprocess based on the multivariate analysis model

Background: Bromide is found naturally in groundwater and surface water. The rapid growth of industrial activities, drainage of surface runoff, and use of methyl bromide in pesticides has increased bromide discharge to the environment. Disinfection of water-containing bromide causes the creation of additional products of organo-halogenated that are considered cancer-causing agents. In this study, the effect and optimization of factors in removal of this ion was evaluated by using the nano-photocatalytic UV/ZnO process. Methods: This analytical study was conducted in a batch system by the phenol-red method. The test design was performed through the analysis model of multi-factor variance with 99 subjects, while the main, interactive, and reciprocal effects of variables, such as reaction time, catalyst concentration, bromide concentration, and pH at different levels of each factor, were analysed by using SPSS version 16. Results: The main, interactive, and reciprocal effects of factors were significant in three different levels with P < 0.001, and the optimal level of the factors reaction time, catalyst concentration, bromide concentration, and pH were 120 minutes, 0.5, 0.1, and 7 mg/L, respectively, by using the Schaffer test. The highest removal efficiency of 95% was obtained at least 91.56 and a maximum of 94.76% was obtained under optimal conditions of all factors. Conclusion: The results show that by optimization of factors, this process can be effectively used to remove bromide from aquatic environments. Keywords: Bromides, Water, Reaction Time, UV/Zn

Adsorption of diazinon from aqueous solutions onto an activated carbon sample produced in Iran

Background: Considering the severe health and environmental hazards caused by the entry of diazinon toxin into water resources, its removal is very important. Given the high costs of imported adsorbents, this research attempted to evaluate, for the first time, the efficiency of Iranian activated carbon in removing diazinon from aqueous solutions. Methods: In this batch experimental study, the effects of contact time (5-90 minutes), adsorbent concentration (0.5-30 g/L), initial concentration of diazinon (5-50 mg/L), and pH (3-10) on the adsorption of diazinon onto the activated carbon were evaluated. Concentrations of diazinon were measured using a high pressure liquid chromatography (HPLC) instrument. The specific surface area of the adsorbent was determined by BET and BJH methods. The experimental adsorption data was analyzed using Langmuir and Freundlich isotherm models. Pseudo first-order and pseudo second-order kinetics models were employed to determine kinetics. Moreover, data was analyzed using SPSS version 19, and Pearson correlation and analysis of variance (ANOVA) tests were performed at a significance level of 0.05. Results: The optimum contact time, sorbent dose, and pH were 30 minutes, 10 g/L, and 5, respectively. The adsorbent could adsorb diazinon with a removal efficiency of 92.5% under optimum conditions (initial concentration: 20 mg/L). The experimental data was better described by the pseudo-second order kinetic and Langmuir isotherm. A maximum adsorption capacity of 71.4 mg/g was calculated by the Langmuir isotherm model.