A batch of lab-based adsorption experiments were performed to investigate the arsenic (As) removal efficacy by activated alumina. Four factors including contact time, pH, initial As concentration and different coexisting ions were examined. The adsorbent made of activated alumina (AA) with particles of 2-4 mm diameter showed a high As removal efficiency and the As concentrations of the samples were below 0.05 mg/L when the hydraulic retention time (HRT) was operated above 5 min. The As concentrations of the samples could remain below 0.05 mg/L for 30 days. A series of AA adsorption dams coupled with several other supporting adsorption techniques were employed for As-contaminated river restoration. The engineering project functioned well, and the effluent As concentration was below 0.05 mg/L when the influent was between 0.2 and 0.7 mg/L, which met the discharge requirement of the Surface Water Quality Standards criteria III in China. The results demonstrated that AA adsorption dams could be applied for emergency treatments of small- or medium-sized rivers contaminated with As.
Iron coated zeolite is made and its adsorption characteristics are compared with activated alumina and zero-valent iron to get further understand of the new adsorbent. The results show that iron coated zeolite removes As(V) in the similar with that by activated alumina with removal rate of 50% in first 5min's adsorption but slower after 60 mins' adsorption and faster than that by zero-valent iron during the whole adsorption process. Iron coated zeolite sorption fits Langmuir model the best. Capacities of activated alumina, iron coated zeolite and zero-valent iron for As(V) adsorption are 7.3mg/g, 3.9mg/g and 3.3 mg/g, respectively. XRD analysis shows that main components on the surface of the used iron coated zeolite in this paper is FeOOH. To improve the adsorption efficiency of iron coated zeolite, diameter of the zeolite should be decreased and iron should be coated more tightly on the zeolite.
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