Excess or lack of levels of nitrate in drinking water is harmful to the human health, the concentration of NO-3 ions must be maintained at 50 mg/l. Donnan dialysis (DD) used as a driving force of the concentration gra...Excess or lack of levels of nitrate in drinking water is harmful to the human health, the concentration of NO-3 ions must be maintained at 50 mg/l. Donnan dialysis (DD) used as a driving force of the concentration gradient is an effective and simple technique for nitrate removal. In this paper, the transport of nitrate through an AMX anion-exchange membrane has been studied as a function of driving ion nature, receiver phase concentration, flow rate, temperature and agitation rate under Donnan dialysis condition. It was observed that the hydrodynamic conditions and temperature were the main variables affecting the transmembrane flow. As the driving ion, the chloride ion is more efficient than the hydrogeneocarbonate ion. The systematic study of the different parameters involved showed that the nitrate removal efficiency obtained with a feed synthetic nitrate solution (62 ppm) was off 96%. This efficiency slightly decreases for a tap water containing the same nitrate concentration;it was about 84%. This can be attributed to the complex ionic composition of the natural water.展开更多
The removal of cadmium（Cd） from synthetic solutions by batch adsorption process was performed using eggshell powder, which is mainly composed of calcite（CaCO3）. In order to optimize the adsorption process, a re- s...The removal of cadmium（Cd） from synthetic solutions by batch adsorption process was performed using eggshell powder, which is mainly composed of calcite（CaCO3）. In order to optimize the adsorption process, a re- sponse surface methodology（RSM） based on Central Composite Design（CCD） was applied. Developed model for Cd removal yields（R, %） response was statistically validated by variance analysis（ANOVA） which showed a high de- termination coefficient value（R2=0.9889）. According to Minitab software, the optimal conditions were found at tem- perature of 44℃, eggshell adsorbent dose of 2.98 g, initial Cd concentration of 36.74 mg/L and initial pH of 7. Under these conditions, the Cd removal yield was 98.76%. The deviation value of 1.24% confirms the validity of the model for the adsorption process optimization. The adsorption isotherm has been described by a Freundlich model. In addition, the predominant sorption mechanisms are the chemisorptions or precipitation（non-reversible） and ion ex- change（reversible）.展开更多
文摘Excess or lack of levels of nitrate in drinking water is harmful to the human health, the concentration of NO-3 ions must be maintained at 50 mg/l. Donnan dialysis (DD) used as a driving force of the concentration gradient is an effective and simple technique for nitrate removal. In this paper, the transport of nitrate through an AMX anion-exchange membrane has been studied as a function of driving ion nature, receiver phase concentration, flow rate, temperature and agitation rate under Donnan dialysis condition. It was observed that the hydrodynamic conditions and temperature were the main variables affecting the transmembrane flow. As the driving ion, the chloride ion is more efficient than the hydrogeneocarbonate ion. The systematic study of the different parameters involved showed that the nitrate removal efficiency obtained with a feed synthetic nitrate solution (62 ppm) was off 96%. This efficiency slightly decreases for a tap water containing the same nitrate concentration;it was about 84%. This can be attributed to the complex ionic composition of the natural water.
文摘The removal of cadmium（Cd） from synthetic solutions by batch adsorption process was performed using eggshell powder, which is mainly composed of calcite（CaCO3）. In order to optimize the adsorption process, a re- sponse surface methodology（RSM） based on Central Composite Design（CCD） was applied. Developed model for Cd removal yields（R, %） response was statistically validated by variance analysis（ANOVA） which showed a high de- termination coefficient value（R2=0.9889）. According to Minitab software, the optimal conditions were found at tem- perature of 44℃, eggshell adsorbent dose of 2.98 g, initial Cd concentration of 36.74 mg/L and initial pH of 7. Under these conditions, the Cd removal yield was 98.76%. The deviation value of 1.24% confirms the validity of the model for the adsorption process optimization. The adsorption isotherm has been described by a Freundlich model. In addition, the predominant sorption mechanisms are the chemisorptions or precipitation（non-reversible） and ion ex- change（reversible）.
