利用硫氧化菌群和廢棄硫生產生物硫酸提高電鍍污泥中 鎳金屬提取效率

Optimized nickel extraction from electroplating sludge using sulfuric acid produced from sulfur-oxidizing bacteria and waste sulfur

菈葵娥(Ayestas Barahona Raquel)

指導教授 ： 邱瑞宇

國立屏東科技大學/國際學院/熱帶農業暨國際合作系/碩士(2024年)

https://doi.org/10.6346/NPUST202400447

摘要

2023年對鎳使用量已經逐漸追上鎳的開採量，對鎳需求的增加，以及高品質礦源逐漸枯竭。尋找鎳替代來源至關重要。而工業廢料中的電鍍污泥（ES），因含有高濃度之重金屬是具開發價值之替代來源。藉由生物濕式治金法中的間接生物浸出法從ES中回收鎳金屬，利用生物產硫酸（BSA）來溶解重金屬，具有多種優勢，包括提高經濟效益、降低能源消耗和減少二次廢物產生。本研究使用了Alicyclobacillus disulfidooxidans（菌群中主要的硫氧化菌）和廢棄硫來生產BSA，並應用於從ES中回收鎳金屬。本研究目的首先分離A. disulfidooxidans以生產穩定的BSA，接下來以BSA浸出劑能維持低pH值和減少浸出時間來提高從ES中萃取鎳的效率。實驗處裡包括不同的溫度（25°C和45°C）和反應時間；進行多次浸出或連續浸出。硫氧化菌群加入廢棄硫為能源培養液中，通過硫氧化過程以產生BSA。BSA經離心及過濾純化後，以濁度測定法分析硫酸鹽濃度，可在7天內達13,000 mg SO4-2/L，pH值則低於0.69。實驗將BSA加入固液比1%（w/v）孔徑為149 μm顆粒大小之ES進行浸出實驗。以感應耦合電漿光學發射光譜儀（ICP-OES）測定浸出液和沉澱中的重金屬濃度。多次浸出試驗結果顯示，BSA的pH能維持穩定，第一次浸出後，pH值從0.9輕微增加至1.12（25°C）；低且穩定且低的pH值表示不需要再補充酸。在鎳萃取方面，第一輪浸出（1小時）後達到最高提取效率為55%。隨後的浸出顯示提取效率逐漸降低：第二輪7%，第三輪 2%，第四輪1%。連續和延長（24小時）浸出實驗，在25°C和45°C下顯示出相似的提取效率，鎳的平均提取效率分別為66% 和68%。隨後，將連續浸出測試縮短為7小時，並比較了BSA和化學硫酸（SSA）在45°C下的提取效率，在浸出過程中，每小時觀察提取效率的變化；結果發現BSA和SSA的效率相當，BSA的鎳提取效率為57%，SSA為59%。另外結果還發現在所有測試時間的提取萃取效率都一樣，表示浸出反應在第一小時內就達到了平衡。最後的連續浸出測試中，浸出時間縮短為1小時；觀察提取效率隨時間變化；在45°C下，15分鐘內達到最高浸出效率（65%），而在25°C下，30分鐘內達到最高提取效率（65%）；這些結果表示，高溫縮短了達到穩定鎳提取效率所需的時間（即平衡）。然而，延長接觸時間在兩個溫度條件下可達到相似的鎳提取效率。結論是A. disulfidooxidans可以有效地在7天內有效地生產高硫酸鹽含量和低pH值的BSA。此外，它在短接觸時間（15-30分鐘）內有效地從ES中浸出鎳，在45°C和25°C下的鎳提取效率均為65%。此外，在低固液比、小顆粒尺寸和高溫的間接生物浸出有助於保持浸出劑的低pH值並縮短浸出時間。如果接觸時間延長，在較低溫度下的浸出可以達到與高溫相似的結果。未來可研究在相同的溫度和浸出時間， 將BSA應用在不同固液比和顆粒大小ES，可能有助於確定是否可以進一步提高鎳的產量和提取效率。

關鍵字

Alicyclobacillus disulfidooxidans ； 間接生物浸出 ； 生物產硫酸 ； 鎳 ； 電鍍污泥

並列摘要

Today, the rising demand for nickel is causing the depletion of high-grade ores, as the rate of mining production is approaching the rate of consumption. Therefore, identifying alternative sources is crucial for sustainable metal extraction. Industrial waste, such as electroplating sludge (ES), is considered an attractive alternative source due to its high concentration of heavy metals. Metal recovery can be achieved through a biological hydrometallurgical method known as indirect bioleaching, an extraction technique that utilizes biogenic sulfuric acid (BSA) for heavy metal dissolution. This method offers several benefits, including cost-effectiveness, reduced energy consumption, and minimized secondary waste output. In this study, Alicyclobacillus disulfidooxidans (sulfur-oxidizer found in consortium) and waste sulfur were utilized for the production of sulfuric acid and its application in the recovery of metals from waste. Therefore, this investigation aimed to isolate A. disulfidooxidans for the production of a consistent BSA and to optimize nickel extraction rates from ES by maintaining the leaching agent’s low pH and reducing the leaching time. To optimize heavy metal extraction rates, multiple leaching rounds and continuous leaching were tested at distinct temperature conditions (25C and 45C) and contact times. The sulfur-oxidizing consortium, in conjunction with waste sulfur, was employed in the sulfur oxidation process to produce biogenic sulfuric acid. The acid was subsequently purified through centrifugation and filtration. Sulfate concentrations were then analyzed using the turbidimetric method, reaching up to 13,000 mg SO4-2/L over a 7-day period, with pH values as low as 0.69. Leaching experiments were subsequently conducted using an electroplating concentration of 1% (w/v) and a particle size of 149 μm. Heavy metal concentrations (mg/L) in both the leachate and precipitate were quantified by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Results from the multiple leaching rounds demonstrated only minor increases in pH within the biogenic sulfuric acid. After the first leaching round, pH values slightly increased from 0.9 to 1.12 at 25°C. The low and stable pH values suggested that acid replenishment was not needed. In terms of nickel extraction, the highest efficiency was achieved after a single round (1 hour), with a recovery of 55%. Subsequent leaching rounds showed progressively lower extraction efficiencies: 7% in Round 2, 2% in Round 3, and 1% in Round 4. Continuous and extended leaching tests (24 hours) demonstrated similar extraction yields and efficiencies at both 25°C and 45°C, with average nickel efficiencies of 66% and 68%, respectively. Subsequently, continuous leaching tests were shortened to 7 h, and the leaching efficiency of BSA was compared to that of synthetic sulfuric acid (SSA) at 45°C. During leaching, leachate samples were withdrawn at distinct contact hours to observe changes in extraction rates. The tests indicated comparable efficiencies between BSA and SSA, with nickel extraction efficiencies of 57% for BSA and 59% for SSA. These results also demonstrated stable extraction rates across all tested contact points, suggesting that the leaching reactions had reached equilibrium within the first contact hour. A final continuous leaching test was performed with a contact time shortened to 1 h; leachate samples were withdrawn at distinct contact times as well. At 45C, highest leaching efficiency (65%) was achieved within 15 min, whereas at 25C, highest leaching efficiency (65%) was reached within 30 min. These results suggest that higher temperatures shortened the time required to reach stable nickel extraction rates (i.e., equilibrium). However, extended contact time results in similar nickel yields and efficiencies at both temperature conditions. In conclusion, A. disulfidooxidans efficiently produces biogenic sulfuric acid with high sulfate content and low pH values within a reduced oxidation period of 7 days. Additionally, it effectively leaches nickel from electroplating sludge (ES) within a short contact time (15-30 min), achieving nickel extraction efficiencies of 65% at both 45°C and 25°C. Furthermore, conducting indirect bioleaching of ES with low waste concentrations, small particle size, and high temperatures helps maintain the leaching agent’s low pH values and reduces the leaching time. Leaching at lower temperatures under the same conditions can achieve comparable results if the contact time is extended. In future studies, evaluating different concentrations and particle sizes under consistent temperature and leaching time conditions could be beneficial in determining whether nickel yield and efficiency can be further increased.

並列關鍵字

Alicyclobacillus disulfidooxidans ； indirect bioleaching ； biogenic sulfuric acid ； nickel ； electroplating sludge

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