The Canadian mining industry is one of Canada’s largest industrial sectors, creating jobs and a significant contributor to the economy. However, the mining activities can be detrimental to the environment due to the release of pollutants. Mining extensively uses nitrogen-based explosives, creating explosive impacted mining wastewaters (EIMWW) that contains substantial quantities of ammonia which is toxic to fish and thus, it has serious environmental repercussions. Ion-exchange (IE) with zeolite is an effective method for ammonia removal as it is easily automated, has a rapid start-up, is not significantly impacted by cold temperature or toxicity effects. Thus, it is particularly suited for Canadian mines. However, the traditional IE regeneration approach of using high concentration NaCl solutions creates a secondary polluting stream. Chlorine regeneration of ammonia-loaded zeolite appears to be a promising option to avoid such a secondary source of contamination. An evaluation of this option and other alternative regeneration are the main focus of this thesis. This thesis includes two initiatives. The first is a set of multi-cycle column loading and regeneration tests to investigate the feasibility of a zeolite (SIR-600) column for ammonia removal from a synthetic EIMWW, containing K and Ca as competing ions, coupled with regeneration using different concentration of chlorine solutions and combined salt+chlorine regeneration solutions. NaOCl regeneration was quite effective, but it was slower than salt regeneration. During the NaOCl regeneration, the main mechanism appears to be the oxidation of ammonia to nitrogen gas and hydrogen ions, however the Na in the NaOCl solution also seems to have a role in the regeneration. This results in pH levels around 3 for approximately half the regeneration cycles. In the combined salt+chlorine regeneration, the incorporation of the salt leads to more rapid elusion of the three ions presumbaly because of the higher sodium concentration (205 meq/L Na versus 14 meq/L Na). The long-term total ammonia nitrogen (TAN) uptake of SIR-600 regenerated with a NaOCl and NaOCl-NaCl were fairly similar, they varied within a relatively small range (0.185meq/g - 0.202meq/g). Thus, the various regeneration schemes did not impact the TAN uptake. The only apparent limitation of NaOCl regeneration is that it required a longer duration. However, the NaOCl is very promising because it resulted in very similar TAN uptakes, the SIR-600 showed a higher preference for TAN over K and avoided creating an additional process waste stream. The second initiative addressed concerns regarding the long-term integrity of SIR-600 arising from its exposure to low pH solutions during the regeneration. Long-term batch tests were performed to expose SIR-600 to low pH conditions (pH=2, pH=3, pH=4) and the characteristics of this IE material were evaluated. The 3-month low batch exposure experiment showed that pH below 4 decreased the TAN uptake capacity by up to 58%. There was no considerable impact on the surface gravimetric analysis (TGA) and Powder x-ray diffraction (PXRD). The exposure to pH=2 and pH=3 led to breakdown of the outer surface of SIR-600 and the creation of fine particles. It also led to decreases in the BET surface area and a decrease in the TAN uptake proportional to the decrease in the BET surface area. Thus, the exposure to pHs below 4 impacts the durability of SIR-600, so SIR-600 may have to be replaced more frequently. However, regeneration with NaOCl solutions still seems very promising as it avoids the creation of a secondary waste stream.

The mining industry is a significant contributor to the Canadian economy. However, the mining activities can be detrimental to the environment due to the release of pollutants. Ammonia is one of the noxious and toxic contaminants associated with mining, ammonia contamination is created by the oxidizing agent in explosives. The explosives impacted mining wastewater (EIMWW) usually contains ammonia and other metal ions. The ammonia in EIMWW could harm the aquatic environment by the depletion of oxygen and its lethal toxicity to aquatic organisms. Before release to environment, EIMWW needs to be treated with an easy-to-operate method for ammonia removal at the remote mining sites. Ion-exchange (IE) with zeolite is an effective method for ammonia removal that is easy-to-operate, is not significantly impacted by cold temperature or toxicity effects. However, the traditional IE regeneration approach of using high concentration NaCl solutions creates a secondary polluting stream. Chlorine regeneration of ammonia-loaded zeolite appears to be a promising option, an evaluation of this option is the main topic of this thesis. This thesis includes three initiatives. The first is a set of multi-cycle batch loading-regeneration tests to assess the viability of ammonia removal with a commercial zeolite (SIR-600) for the treatment of a synthetic EIMWW (containing total ammonia nitrogen (TAN), K, and Ca) and to examine the performance of different ion-exchange regeneration solutions. The long-term TAN uptake of SIR-600 regenerated using a NaOCl (100 mg free Cl2/L) solution was 0.24 meq/g, which was approximately 20% lower than that after a NaCl regeneration. However, chlorine regeneration is promising because the selectivity of SIR-600 for TAN over Ca and K increased after the chlorine regeneration. To simulate recycling of the NaOCl regenerants, K and Ca were added to the NaOCl solution, it did not substantially affect the subsequent SIR-600’s ion uptake. This initiative represents a significant contribution since the earlier studies into chlorine regeneration did not investigate the impact of competing ions. The second initiative addressed concerns regarding the long-term integrity of SIR-600 arising from its exposure to high chlorine concentrations during the regeneration. The five-week long chlorine batch exposure tests with solutions of up to 1000 mg free Cl2/L showed that chlorine exposure did not significantly affect the SIR-600’s characteristics in terms of particle size distribution, surface area, FTIR spectra and ion uptake. Thus, SIR-600 has the potential for long-term use in field applications. The final initiative evaluated the feasibility of chlorine regeneration for continuous flow IE column systems used for ammonia removal from a synthetic EIMWW. Continuous flow column systems are important because these are the standard IE units used in full-scale applications. Multi-cycle column loading-regeneration tests were performed to compare the zeolite performance using a NaOCl (1000 ppm as free Cl2) solution with that using a 5% NaCl regeneration. The influence of loading duration was also assessed. The use of 6-hr loading cycles were shown to be preferable to 23-hr loading cycles because it had lower effluent concentrations and they could achieve higher overall TAN mass removals per unit time. After three operational cycles, the SIR-600 had similar TAN uptake performances (0.21 meq/g Vs. 0.21 meq/g) after NaOCl regeneration and after salt (NaCl) regeneration. This is in contrast to the lower TAN uptakes for the NaOCl regeneration in the batch tests, this indicates that batch tests are not always representative of full-scale applications. Compared to NaCl regenerated SIR-600, SIR-600 after NaOCl regeneration had a higher preference for TAN over Ca and K, which makes this type of regeneration very promising. Its only apparent limitation is that the NaOCl regeneration required a longer duration. During the NaOCl regeneration, the main mechanism appears to be the oxidation of ammonia to nitrogen gas and hydrogen ions, however the Na in the NaOCl solution also seems to have a role in the regeneration.