EXPERIMENTAL INVESTIGATION OF THE CHEMICAL REDUCTION OF NITRATE IN WATER BY Mg° AND Cu/Mg BIMETALLIC PARTICLES IN THE ABSENCE OF ANY PH- CONTROL MECHANISM

摘要

Batch experiments revealed that magnesium (Mg°) and copper/magnesium (Cu/Mg) particles had the potential for being used in the removal of nitrate from aqueous solutions. This study suggested that the reductive denitrification of nitrate by Mg° and Cu/Mg bimetals depended on a number of parameters including reductant dose, solution temperature, initial nitrate concentration and contact time. The values of the activation energy (E_a) of nitrate reduction over a temperature range of 5-60 ℃ were 20.39, 20.34, 12.77 and 12.13 kJ/mol for Mg°, 0.1% Cu/Mg, 1% Cu/Mg and 5% Cu/Mg, respectively. The predominant by-product depended strongly on the initial pH of the solution and the reductant type. When the initial pH was 4, Mg° produced more nitrite and ammonium than the Cu/Mg bimetals. The time required for the removal of 70% of NO3~-_3 from a 100 mg/L solution was about 80 min when the experiments were conducted using Mg° particles and it was about 5 min when the reaction was conducted under the same conditions using bimetallic 1% Cu/Mg. Thus, bimetal Cu/Mg had a greater potential for being used as a reductant during the denitrification of water in comparison with Mg° as far as the generation of toxic by-products is concerned.