Abstract
This manuscript addresses the treatment explosives-impacted mining wastewaters (EIMWW) using ion-exchange to remove elevated levels of ammonia. Repeated batch loading-regeneration cycles were conducted for two commercially available zeolite media used in the treatment of ammonia-ladenEIMWW to establish the effects of competing ions and regeneration solution composition. The Northern Ontario EIMWW tested contained 3.87 meq/L total ammonia (TA) as well as 2.85 meq/L Kþ and 3.9 meq/L Ca2þ.The media studied were a natural clinoptilolite and a modified clinoptilolite (SIR-600). Five regenerant solutions with different NaCl and KCl concentrations were evaluated. The presence of potassium in the regenerant was found to hinder the TA exchange capacity of both zeolites. The SIR-600 and the natural clinoptilolite used in conjunction with the 10% NaCl solution featured the best TA exchange capacities, 0.46 ± 0.02 meq TA/g and 0.36 ± 0.05 meq TA/g, respectively. The batch tests showed that both media had a slight preference for Kþ over TA. The continuous flow column tests performed using SIR-600 media greatly accentuated the selectivity of Kþ over TA. In reaching the same 0.55 meq TA/L breakthrough level, the same modified zeolite column was able to treat five time more volume of a synthetic TA solution than EIMWW.
Highlights
The mining industry extensively uses nitrogen-based explosives, with ammonium nitrate mixed with fuel oil (ANFO) being the primary blasting agent
The batch exchange/regeneration/ion-exchange experiments showed that regenerating both zeolites using KCl solutions resulted in smaller total ammonia (TA) uptake capacities from explosives-impacted mining wastewaters (EIMWW) compared to the NaCl solutions
The regeneration with the 5% and the 10% NaCl solution resulted in the highest TA batch test uptakes, and the modified clinoptilolite had higher TA uptake from EIMWW than the clinoptilolite
Summary
The mining industry extensively uses nitrogen-based explosives, with ammonium nitrate mixed with fuel oil (ANFO) being the primary blasting agent. Transformation of amines in flotation circuits, pH regulation agents, ammonium sulphate as eluent of uranium from ion exchange resins, ammonium hydroxide used in uranium precipitation, and ammonia used to recover copper and nickel in hydrometallurgical processes are other sources of ammonia in mining water [1e4]. These result in mining effluents containing elevated concentrations of ammonia. There are an increasing number of ammonia discharge regulations around the world to curb the discharge of ammonia into the environment [5e8] This has led to the research and development of multiple treatment options for the removal and/or transformation of ammonia, while aiming to minimize subsequent environmental consequences. Biological nitrificationdenitrification, which is quite common in domestic wastewater treatment, is not the best choice for mining wastewater treatment because it is significantly impacted by low temperatures, it does not perform as well when there are large fluctuation in the influent ammonia
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