This study compared the methylene blue (MB) removal from aqueous solution by natural bentonite (Bent) and cement kiln dust (CKD). Bentonite and CKD were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), Brunauer Emmett Teller (BET) specific surface area, Fourier transform infrared (FTIR), and scanning electron microscopy (SEM). The comparison between bentonite and CKD in the removal of MB dye was investigated in different conditions including initial MB concentration, adsorbent doses, pH, salt concentration, and temperature by batch experiments. Adsorption kinetics results were fitted with fractional power, Elovich, pseudo-first-order, pseudo-second-order, and intraparticle diffusion equations. The pseudo-second-order model was well fitted for experimental results at the different tested initial concentrations (50-300 mgMB/L). Equilibrium adsorption data were evaluated by Freundlich and Langmuir and Temkin models. The experimental results fitted very well by the Langmuir isotherm model. Bentonite exhibited the largest adsorption capacity (3257.33 mg/g) than CKD (2150.54 mg/g). Increasing the temperature from 298K to 323 o K convinced an increase of the adsorption of MB dye by both sorbents and the process was found to be endothermic and spontaneous. The obtained results indicated that both adsorbents are efficient and low-cost adsorbents for effective removal of MB dye with privilege in the efficiency for bentonite and with no cost for CKD.
This study investigated the removal of imidacloprid (IMI) and oxamyl (OX) pesticides by cement kiln dust (CKD) as industrial by-products. CKD was identified by elements composition, Fourier-transform infrared (FTIR), and scanning electron microscopy (SEM). Effects of initial concentration (100-2000 mg/L), and contact time (10-360 min) were investigated. The kinetic results of IMI and OX pesticides were fitted to pseudo-first-order, pseudo-secondorder, and intra-particle diffusion equations. The pseudosecond-order kinetic model fitted well for IMI removal, while pseudo-first-order kinetic model flitted to OX removal results. Isotherm results were examined by different isotherm models (Freundlich, Langmuir, and Temkin equations). The results fitted well with the Langmuir isotherm model (R 2 =0.988 and 0.999) with maximum adsorption capacity of 142.85 and 100.00 mg/g for IMI and OX pesticide removal by CKD, respectively. The obtained results indicated the potential of using CKD as an efficient and, low-cost adsorbent for the removal of IMI and OX pesticides from aqueous solutions.
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