A. Morshedi - Soil Science department of Shahid Bahonar, university of Kerman
HM Naghibi - B. S student of chemical engineering of Shahid Bahonar, university of kerman

Manganese and zinc are important metals at low levels, because many health hazards are associated with them. Their removal from contaminated samples is of utmost importance. The technique of adsorption using various economically viable adsorbents such as rice husk ash and sawdust has been applied for their removal from aqueous solutions. Various parameters such as contact time, initial pH and metal ion concentrations were studied, optimized and applied to the present study. The obtained equilibrium data was analyzed in the linear model of Freundlich and Langmuir isotherms. Results revealed that rice husk ash is most efficient in removing zinc and manganese from drinking or irrigation water in comparison to the sawdust adsorbent. The rice husks were supplied by the Mazandran Region (Iran). A weighed amount of the washed and dried rice husks were packed into the gas furnace and rice husk ash was obtained by burning rice husks below 300ºC and the ash contained high active carbon. The maximum removal took place in the pH range of 3.5-6.5 for manganese and range of 3.5-5.5 for zinc, contact time of 60 min and initial concentration of 10 g L-1 of rice husk ash adsorbent. Studies showed that both the Langmuir and Freundlich models fitted with results with R2 >0.90. The study showed that10 g L-1of rice husk ash caused maximum removing of 42 and 51 mgL-1 of Mn and Zn respectively from test solutions.

Rice husks, Heavy metals removal, Contact time, Rice husk ash