鈷因具備優異的電化學活性，被廣泛應用於鋰離子電池電極材料、硬質合金及催化劑等產業，然而，這項戰略性關鍵原物料，恐由於國際情勢不穩定以及出口政策的改變，導致供應鏈中斷。
為避免此等情事發生，因此本研究採用流體化床均質結晶技術(Fluidized-Bed Homogeneous Crystallization, FBHC)具備常溫常壓操作、低含水率及產出高純度顆粒之優點，將此戰略性關鍵原物料進行回收，並將其轉化為具備應用潛力的氫氧化鈷(Co(OH)2)。
研究首先透過瓶杯試驗(Jar-test)初步探討Co2+在不同pH環境下的沉澱行為中觀察到在強鹼環境下，沉澱物極易受溶液中溶解氧影響，發生相轉變，氧化為三價的鹼式氧化鈷(CoOOH)，導致產物結晶度下降且結構混亂。為抑制氧化現象並提升產物純度，本研究進一步最佳化FBHC之操作參數。結果顯示隨著pH值上升，去除率與結晶率隨pH提升而增加，直至過飽和度大於10後，過高的過飽和度將導致均相成核大量發生，致使結晶率大幅下降，在以調整進料濃度控制的截面負荷變因也同樣觀察到此現象的發生，因此應將過飽和度控制在10以內，且CCo,i = 500±10 mg-Co/L, pHe = 9.2±0.2, HRT = 32 min, H = 30 cm, U = 25.27 m/h, LCo = 0.517 kg/m2h, R = 12.8的操作條件下，系統可維持穩定操作，總鈷去除率(TR)與結晶率(CR)分別達99.8%與98.3%，僅產生少量的汙泥，且98.3%的鈷皆已成功回收。
後續成分鑑定鈷含量為63.0 wt%，且產物主成分為β-Co(OH)2，含水率僅3.56%。本研究證實FBHC技術可透過精準的調控過飽和度，避免均相成核產生大量汙泥，同時回收β-氫氧化鈷(比表面積32.2897 m2/g，孔隙率48.2%)，為含鈷廢水的資源化提供具體之技術依據。

Cobalt, due to its excellent electrochemical activity, is widely used in lithium-ion battery electrode materials, hard alloys, and catalysts. However, this strategically critical raw material is at risk of supply chain disruptions due to international instability and changes in export policies. To avoid this, our laboratory proactively deployed fluidized-bed homogeneous crystallization (FBHC) technology, which offers advantages such as room temperature and pressure operation, low water content, and high-purity particle production, to recycle this strategically critical raw material and convert it into high-value-added cobalt hydroxide (Co(OH)2).
The study first explored the precipitation behavior of Co2+ under different pH conditions through a jar-test. It was observed that under strongly alkaline conditions, the precipitate is highly susceptible to dissolved oxygen in the solution, undergoing a phase transition and oxidizing to trivalent basic cobalt oxide (CoOOH), resulting in decreased crystallinity and a disordered structure. To suppress oxidation and improve product purity, this study further optimized the operating parameters of FBHC. The results showed that as the pH value increased, both the removal rate and crystallization rate remained stable and positively correlated with the solubility curve. However, once the supersaturation exceeded 10, excessive supersaturation led to a large amount of homogeneous nucleation, resulting in a significant decrease in crystallization rate. This phenomenon was also observed when the cross-sectional load was controlled by adjusting the feed concentration. Therefore, the supersaturation should be controlled below 10. Under the operating conditions of CCo,i = 500±10 mg-Co/L, pHe = 9.2±0.2, HRT = 32 min, H = 30 cm, U = 25.27 m/h, LCo = 0.517 kg/m2h, and R = 12.8, the system could maintain stable operation, achieving a total cobalt removal rate (TR) of 99.8% and a crystallization ratio (CR) of 98.3%, with only a small amount of sludge produced, and 98.3% of the cobalt successfully recovered.
Subsequent component identification confirmed a cobalt content of 63.0 wt%, with β-Co(OH)2 as the main component and a water content of only 3.56%. This study demonstrates that FBHC technology can not only remove cobalt ions from wastewater, but also avoid the generation of large amounts of sludge through precise control of supersaturation. Simultaneously, it recovers 98.3% of β-cobalt hydroxide (BET surface area 32.2897 m2/g, porosity 48.2%), providing concrete technical support for the resource utilization of cobalt-containing wastewater.

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