Total hardness (TH) of water causes numerous problems in life and industry, that shows the necessity of water hardness removal. In this research, different SORBENTS such as almond shell, wheat husk, rice husk, sawdust, zeolite, bentonite and activated carbon in raw state, acid-activated and alkaline-activated conditions for removing Ca, Mg and therefore, water hardness were used. The results of this study showed that some of SORBENTS needed to be activated by acid or base to remove calcium, magnesium and hardness of the brine solution in different salinities. In salinity of 20 dS m-1, acidic-activation of rice husk, sawdust, zeolites and activated carbon increased Mg removal from saline water. In this salinity, alkaline-activation of almond shell and bentonite and likewise acidic activation of wheat and rice husk enhanced Ca removal from saline water. Moreover, alkaline activation of almond shell and bentonite and likewise acidic activation of sawdust, wheat and rice husk caused reduction of saline water hardness. Removal percentages of calcium, magnesium and hardness for salinity of 9 dS m-1 were greater than those for the salinity of 20 dS m-1.

In present paper two agricultural residues, rice hull, sawdust and a soil sample were examined as SORBENTS to remove heavy metals Pb(II), Cd(II), Cu(II), Zn(II) and Ni(II) from synthetic solutions. The SORBENTS were analyzed for some physico-chemical characteristics as CEC, surface area and elemental composition using ammonium acetate method, N2-BET and SEM-EDX respectively. The effect of initial pH and concentration of solutions, type of SORBENTS, equilibrium time and particle size of SORBENTS were studied in removal of heavy metals from metal solutions. The sorption experiments were carried out in 1:100 suspensions of sorbent to synthetic solutions. The sorption of the heavy metals from the synthetic solutions was increased with pH for all SORBENTS, significantly (p< 0.01). pH=5 was selected as the lowest pH with highest mean sorption. At this pH, among the heavy metals, Pb(II) and Cd(II) showed the highest sorption with the average of 0.87 and 0.77 mg/g and then Cu, Zn and Ni, respectively. The increase of metal concentration in the solution increased the sorption. The sorption isotherms of the natural SORBENTS and the soil sample were best described by the Freundlich model. The highest sorption capacity was observed for the soil sample, followed by the rice hull and the sawdust samples, respectively. The sorption of the heavy metals from the synthetic solutions was increased with increasing of shaking time. Shaking time of 60 minutes was considered as equilibrium time. Decreasing of sorbent particle size increased the sorption. The smallest diameter of particles (< 0.5 mm) showed the highest sorption capacity.

Sodium carbonate (Na2CO3) supported by gamma-alumina (-Al2O3) is one of the best SORBENTS for CO2 capture in economic terms because of its low raw material cost and excellent performance in low-temperature operation. The fundamental goal of this study is to optimize the operating conditions of CO2 adsorption by Na2CO3/Al2O3 sorbent in a fixed bed reactor. The sorbent characterization was studied using BET, SEM, XRF, and XRD analyses, and the sorbent structure was compared before and after the carbonation reaction. Moreover, the effects of side reactions on the adsorption process were investigated. The Response Surface Methodology (RSM) was used with Box-Behnken Design (BBD) to design the experiments. The optimum conditions are introduced at the point where initial CO2 capture capacity and deactivation rate constants are as high and as low as possible, respectively. The optimum values of the variables corresponding to the temperature of 50° C, vapor pretreatment time of 9 min, and H2O/CO2 mole ratio of 1. The amounts of initial CO2 capture capacity and deactivation rate constant in the optimum conditions were obtained to be 39. 238 mgCO2/gsorbent and 0. 416 min-1, respectively.

Arsenic is known as a potential threat to the environment. Therefore, this research aims to assess the arsenic removal efficiency from an aqueous solution, by a novel bio- sorbent based on the Sour-Lemon Peel (SLP). To treat SLP, a combination of two methods (treated with mineral acids and high temperature) was used, and a designed bio-sorbent called SLP-activated/ carbonized. The SLP-activated and SLP- carbonized were also prepared using hydrochloric acid (HCl) and 400°C temperature, respectively, to compare the results of each of the three methods. Afterward, adsorption parameters such as pH, initial ion concentration, bio-sorbent dosage, contact time, and temperature were assessed. It was found that the combination method has provided a higher adsorption capacity so that, up to ~99% arsenic removal was observed with SLP-activated/carbonized at pH of 7.0 and 40°C. The adsorption capacities for SLP- carbonized and SLP-activated were 87.92% (pH:7, 60°C) and 78.50% (pH:6, 90°C), respectively. Moreover, adsorption kinetics data indicated the best fit with the pseudo-second-order model. The maximum bio-sorption capacity by the Langmuir isotherm model was also recorded for SLP-activated/carbonized (53.47 mg/g). Notably, arsenic adsorption on studied bio-SORBENTS takes place spontaneously and through chemisorption along with the endothermic nature of the bio-sorption process and reduction of random collisions in the solid-liquid phase.