The effects of process parameters in the removal of arsenic using treated laterite as adsorbent

Arsenic contamination in groundwater has become a serious problem around the world including Thailand, especially in the southern area of Nakron Sri Thammarat Province. Adsorption technique using a local, cheap and efficient adsorbent is a feasible approach for the treatment of arsenic from drinking well or/and groundwater. The gray-colored laterite which is locally available in Palawan, Philippines gave the highest removal for arsenic after treating the laterite with 30%HCl and calcined at 700°C. In this study, the treated laterite was used as an adsorbent for arsenic adsorption from simulated groundwater. Effect of adsorbent dose, initial pH and initial arsenic concentration on the removal of arsenic were investigated. The results showed that the adsorbent dose was 25 g/L and pH of solution at 7(0.2) gave the highest adsorption capacity with a percent removal of 98.74% from arsenic concentration of 296.63 ppb in groundwater. The Freundlich isotherms and pseudo-second order described well the equilibrium and kinetics of arsenic adsorption process of simulated groundwater using treated laterite 30%HCl and calcined at 700°C under batch experimental conditions. The maximum adsorption capacity was found to be 0.031 mg As/g adsorbent. Hence, treated laterite is an effective adsorbent to remove arsenic from groundwater and could be used by people living in rural areas such as Thailand and other Asian Countries

Single-step process without organic template for the formation of zeolite A from RHA

Dice-shaped zeolite A (NaA) was prepared via direct dissolution of rice husk ash (96.5% SiO2) in the presence of NaOH and sodium aluminate solution by autoclave process at 90 degrees C/6 h without using any templating agent. The prepared particles were characterized by DTA/TG, XRD, FTIR, N-2 adsorption-desorption physisorption analysis, FESEM, and TEM. XRD results confirmed crystallization of pure NaA zeolite phase. FTIR study shows the characteristic bands at 554 cm(-1) for double 4 membered ring (D4R) of NaA zeolite. The total BET surface area of the product was found to be 31.6 m(2) g(-1). FESEM and TEM images show dice shaped NaA particles of size around 1 mu m which is formed via oriented crystalline aggregation of primary particles (30-40 nm). A tentative mechanism was proposed for the formation of NaA crystals through direct dissolution of rice husk ash. The synthesized NaA zeolite could be used for purification of alcohol and separation of toxic and radioactive ions from waste water via a cost-effective process