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Lead Adsorption from Industrial Wastewater Using Rice Husk Ash

Over the course of recent decades, industrial and agricultural activities have led to a considerable increase in waste materials. Rice husk ash (RHA), an agricultural waste, is produced about 100 million tons annually in the world and 0.45 million tons in Iran. Due to growing environmental concerns about disposal of these wastes, efforts are required to apply the wastes in industry. On the other hand, heavy metals are one of the main groups of environmental pollutants. Discharge of industrial wastewater, with high concentration of heavy metals, to surface water and groundwater could pollute the environment. Adsorption process is one of the available methods of treating wastewater containing heavy metals such as lead. The high cost of common adsorbents such as activated carbon has inspired a search for suitable low-cost adsorbents. The aim of this study was removal of lead using RHA as low cost adsorbent from industrial wastewaters. In this research in order to burn the husks at a controlled temperature and atmosphere and to obtain a highly reactive RHA, a furnace was designed and built. For each experiment, 100 mL wastewater was mixed with I and 3 grams of RHA (burnt at temperatures of 250, 350 and 450°C) and two contact times (5 and 60 min.) The results showed that the percent of adsorption increased with increasing the amount of RHA and contact time (P<0.05). Also, burnt RHA at lower temperature in furnace, showed better performance. The results revealed that pH of wastewater increased with increasing the amount of RHA. Produced RHA at higher temperature increased pH more than other treatment.