, , , ,
Volume 18, Issue 68 (9-2014)
Abstract
Zeolite is widely used for removing heavy metals from aqueous solutions. The objective of this study was to assess three sizes of zeolite in removing lead, nickel and cadmium from wastewater. A splite-plot experimental design was employed with 45 treatments and three replications at Shiraz University Lab in 2011. The treatments were five different concentrations of the pollutant and three sizes of zeolite (0.075, 0.2 and 0.425mm). The concentrations for lead were: 40, 250, 500, 1000 and 1250 mg/l and 4, 6, 15, 20 and 40 mg/l for nickel and cadmium. The results showed that the effect of concentrations of pollutant was significant, and by increasing the concentration of pollutant, absorption of heavy metals by zeolite increases linearly. Maximum lead absorption occurred at 1250 mg/l with 59.97 mg and minimum absorption of lead was related to the concentration of40 mg/l with 1.82 mg for 1 grams of zeolite. Maximum and minimum nickel absorptions were related to the concentration of 40 and 4 mg/l with 1.92 and 0.16 mg for 1 grams of zeolite, respectively. The values were 1.87 and 0.18 mg for 40 and 4 mg/l for cadmium, respectively. The effect of size of zeolite on the pollutant adsorption was not significant.
J. Abedi Koupaei, Z. Iravani,
Volume 27, Issue 1 (5-2023)
Abstract
Water pollution with petroleum products is one of the serious environmental problems in Iran. According to the importance of this issue, refining benzene by bio-absorbent has attracted much attention in recent years. The maximum permissible limit assigned by World Health Organization (WHO) for benzene in drinking water is 0.001 mg/L. In recent years, attempts made to develop inexpensive adsorbents utilizing abundant natural materials. Agricultural waste materials often employed as adsorbent may have potential marketing preference for wastewater treatment among other adsorbent types due to the low cost, environmentally friendly, naturally accessible, and efficiency. The objective of this study was to investigate the removal of benzene by batch and continuous techniques. In this study, the ash cone pine (APC) was used for the removal of benzene from aqueous solutions and its ability as an adsorbent, while the variable initial concentration of benzene, the amount of adsorbent, contact time, temperature, and pollutant's solution pH were investigated. Langmuirand and Freundlich Isotherm models were fitted to benzene adsorption equilibrium data. Kinetic models including pseudo-first order, pseudo-second order, intra-particle diffusion, and power function were used to describe kinetic data of benzene adsorption. The results showed that optimum benzene adsorption was observed at pH=7, and the optimum amount of adsorbent was 0.1 g. The observed equilibrium time was 10 minutes. The equilibrium adsorption capacities were 366 mg/g at 2000 mg/L initial benzene concentration. Linear and non-linear isotherm studies showed that equilibrium data better fitted the Langmuir isotherm model. Kinetic studies showed better applicability of the pseudo-second-order kinetics model. Column adsorption experiments were performed to check the absorbent performance during continuously injecting benzene solution into the adsorbent column until the adsorbent has been saturated to complete the studies on the introduced adsorbent. The results for columns with continuous inflow indicated that the maximum capacity of adsorption of benzene for the adsorbent column with a diameter of 3cm, and input concentration of 1000 mg/L, and an input rate of 100 mL/h for ash cone pine (APC) was 295 mg/g. The results of this experiment showed that APC has a high capability for the removal of benzene from aqueous solutions.
