本研究以自行製備的氧化鐵纖鐵礦（Lepidocrocite）與針鐵礦（Goethite）探討對水中二價銅離子之吸附情形。
首先以自行合成之氧化鐵進行X光繞射儀（XRD）鑑定其物種確實為纖鐵礦和針鐵礦，再藉由電子顯微鏡（FE-SEM）、能量散佈光譜儀(EDS)、比表面積（BET）和界達電位（Zeta meter）分析，了解氧化鐵之相關特性。
批次試驗結果得知，在水中二價銅離子起始濃度0.2 mmol/L、起始pH值6.0進行之吸附動力實驗，針鐵礦吸附平衡時間約120分鐘、纖鐵礦約360分鐘，平衡時間吸附量大小依序為針鐵礦 (56 mmol/kg ) > 纖鐵礦 (28 mmol/kg)，而氧化鐵吸附水中二價銅離子的過程較符合擬二階反應，其反應速率為針鐵礦 (0.006 kg/mmol-min) > 纖鐵礦 (0.002 kg/mmol-min)。吸附平衡實驗結果顯示針鐵礦於pH值> 4時，對水中二價銅離子均有很高的吸附效率；纖鐵礦則隨著二價銅離子起始濃度、pH值、溫度、背景離子及吸附競爭物質濃度(硫酸鹽、磷酸鹽)提升而增加吸附量，而pH值為影響氧化鐵對水中二價銅離子吸附之重要因子。吸附等溫Freundlich模式均適合模擬兩種鐵礦對水中二價銅離子之吸附效應；由熱力學計算結果得知吸附自由能△G與焓值△H，顯示氧化鐵吸附水中二價銅離子大部分為自發性吸熱反應，而針鐵礦在pH值 > 4.5為放熱反應。 The aim of this study is to reveal the adsorption phenomena of copper ion onto lepidocrocite and goethite.
The surface properties of both lepidocrocite and goethite were analyzed with X-ray dfffraction (XRD), scanning electronic microscopy (SEM), energy dispersive spectrophotometer(EDS), specific surface area analyzer (BET), and zeta meter.
The tests, conducted at initial pH of 6.0 and 0.2mmol/L of initial copper concentration, showed that to reach adsorption equilibrium of copper ion onto lepidocrocite needed about 360 miuntes, whereas about 120 miuntes for goethite. The sequence of equilibrium adsorption capacity for copper ion was goethite (56 mmol/kg)>lepidocrocite (28 mmol/kg).Copper ion adsorbed onto iron oxides followed the pseudo-second-order rate equation. The sequence of adsorption rate constants was goethite (0.006 kg/mmol-min)>lepidocrocite (0.002 kg/mmol-min).
Results also reveal that goethite showed a higher efficiency for adsorbing copper ion at a pH value of higher than 4.0. The amount of copper ion adsorbed increased with increasing initial concentration of copper ion, pH, temperature, ionic strength, adsorption competition (sulfate and phosphate) for lepidocrocite. Freundlich isotherm equation can be used to describe the adsorption capacity for the adsorption of copper onto both lepidocrocite and goethite. The pH value was one of the important factor in this study. Isotherm adsorption data can be used to determine the thermodynamic parameters (free energr change (△G) and enthalpy change (△H)) of the adsorption process. Based on these thermodynamic parameters, we can find that most of the reactions of copper ion adsorbed onto iron oxides might be spontaneous and endothermic. However, copper ion adsorbed onto goethite would be exothermic at a pH value of higher than 4.5.
