本研究主要以硼氫化鈉(NaBH4)來還原廢水中高濃度的硝酸根離子,探討硝酸鹽氮於不同實驗條件下之去除效果。實驗係以藥品級硝酸鈉(NaNO3)粉末配製模擬高濃度硝酸根之廢水,並加入不同添加量之硫酸銅(CuSO4)或氫氧化銅(Cu(OH)2)作為反應之起始劑,其中部分樣品利用5N氫氧化鈉(NaOH)水溶液調整其溶液之酸鹼濃度,再加入不同添加量之硼氫化鈉後,在60℃下反應一小時,記錄pH值與氧化還原電位(ORP)之變化。然後利用離子層析儀(Ion chromatography)檢測反應後溶液中殘留之硝酸根與亞硝酸根之濃度,探討硫酸銅 、氫氧化銅與硼氫化鈉用量以及溶液的酸鹼值對去除硝酸根之影響。此實驗可處理高達11297ppm之模擬硝酸根濃度廢液,當以硫酸銅為起始劑時,其去除率可達81%;而在某些濃度的試樣,加入硫酸銅後再調整pH至鹼性或將起始劑改成氫氧化銅時,其硝酸根離子之去除率可高達九成甚至達到完全去除的地步。本研究結果發現,此實驗在沒有加入起始劑的情況下,利用硼氫化鈉當還原劑之反應無法順利還原硝酸根。在不同pH值的條件下,pH值為10之鹼性溶液較無調整者有更佳的硝酸鹽氮之去除能力。另一方面在相同酸鹼值之條件下,當硝酸根起始濃度越來越高時,可以看出硫酸銅為起始劑時,其硝酸根的去除效果與氫氧化銅為起始劑時效果差異不大,但在成本上的考量以及藥品取得方便的情況下,選擇硫酸銅為此反應之起始劑為最佳的選擇。
In this study, sodium borotryhydride (NaBH4) was used to reduce the wastewater containing nitrate in high concentration. Experiments were conducted by preparing sodium nitrate(NaNO3) solution in high concentration as simulated wastewater, followed by adding different amounts of copper sulfate(CuSO4) or copper hydroxide(Cu(OH)2) as the catalyst for this chemical reaction. Keeping the solution in the temperature of 60℃ for one hour and observed the pH value and oxidant reduction potential (ORP) change. The sodium hydroxide(NaOH) solution with the concentration of 5N were selectively been added into some samples to adjust the solution into an alkaline condition with a pH value of 10. Ion chromatography(IC) was been chosen to detect the nitrate and nitrite concentration in the solution. Different amounts of CuSO4, Cu(OH)2, and NaBH4, were investigated to find the removal effect of nitrate, as well as the pH and ORP value in the solution. This experiment can treat the simulated wastewater with the concentration up to 11297ppm. When the CuSO4 was been added as the catalyst, the nitrate removal rate was up to 81%. In some samples which were been added CuSO4 and then adjusted the pH value to alkali or used Cu(OH)2 as the catalyst, the removal rate of nitrate was up to 90% or even complete removal. The nitrate and nitrite reduction could not be happened without the addition of Cu(OH)2 or CuSO4. The removal rate of nitrate would get better by adjusting pH to the higher level. When the initial concentration of nitrate is getting higher, the removal rate of nitrate would almost the same by adding CuSO4 or Cu(OH)2. But by considering the cost and availability, CuSO4 would be the best choice as the catalyst in this NaBH4 reduction reaction.