Iranian Journal of

Background and Objectives: Nowadays nitrate concentrations in surface water and especially in groundwater have increased in many locations in the world. Since nitrates cause many health and environmental concerns, increased nitrate concentrations in groundwater have led to rendered aquifers unusable as water sources. So, as the water demand is still increasing the throughout the world, decreasing the nitrate concentration in drinking water is imperative. Magnesium powder has been determined to be potentially useful for the removal of nitrate in the water environment. This research is aimed at subjecting the kinetics of nitrate chemical reduction by Mgo to an analysis of some factors affecting the chemical denitrification.
Materials and Methods: Nitrate concentrations determined in 220 nm using a spectrophotometer.To determine the performance of nitrate removal by Mg0 powder, double distilled water was used for preparation of reagents and simulation of contaminated water with nitrate.All experiments were triplicate and the averaged results were reported.
Results: Kinetics analysis from batch studies revealed that the denitrification reaction with Mgo powder appeared to be a first-order with respect to substrate and the observed reaction rate constant (kobs). The effects of mixing intensity on the denitrification rate suggest that the denitrification appears to be coupled with oxidative dissolution of magnesium through a largely mass transportlimited surface reaction. Also in the denitrification by Mgo determined that Mgo dose related with kobs ( R2>0/99 )S
Conclusion: In this research was determined that denitrification effectively by Mg0 powder can achieved in a wide range of concentrations under atmospheric conditions and without pH controlling within short reaction time. Denitrification rate was related to some parameters such as contact time, Mgo dosage, mixing rate and initial nitrate concentration.

Backgrounds and Objectives: High level of nitrate ion in the water resources cause some health and environmental problems. The aim of this research is to study nitrate removal by Zero-Valent Magnesium (ZVM) and MgCl2-modified pumice from aqueous solutions.
Materials and Methods: The pumice granules were modified by MgCl2 . The removal of nitrate was studied in a batch system. The pH, initial nitrate concentration and sorbent mass parameters and the Langmuir and Freundlich models were studied in the sorption of nitrate onto the pumice. The ZVM was also used in a bach system and the previous parameters were studied.
Results: The removal efficiencies of nitrate by ZVM at the the initial pH of 3, 5 and 7 with controlling the pH were 70%, 40% and 30% ,respectively. These values are much higher than the values of the condition during which the pH was not controled. The nitrate removal efficiency increased by increasing of initial nitrate concentration in a constant molar ratio of Mgo/NO3. The removal efficiencies of nitrate by the modified pumice at the the initial pH of 3, 6.5 and 10 (when pH kept under control) were 49%, 29% and 16%, respectively. By increasing of the initial nitrate concentration the removal efficiency increased. The values of R2 for the Langmuir and Freundlich models were 0.944 and 0.810, respectively. The sorption process Fitted well the Langmuir model with a monolayer sorption capacity of 0.68 mg/g.
Conclusion: The modified pumice had lower efficiency than ZVM in the removal of nitrate ion and its usage is not considerably affected bye the pH in comparison with ZVM. The pH of the solution should be cansiderd as a main controling parameter to get an optimum efficiency in the nitrate-ZVM process.