Removal of Aqueous Hexavalent Chromium by Nano Copper-Resin

本研究利用陽離子交換樹脂負載奈米零價銅(nano copper-resin)，將六價鉻Cr(Ⅵ)還原成三價鉻Cr(Ⅲ)。陽離子交換樹脂可作為奈米零價銅的分散劑，以避免奈米零價銅在溶液中聚集成塊而降低反應表面積；此外，陽離子交換樹脂亦可回收反應後的二價銅離子(Cu2+)與三價鉻離子(Cr3+)。 本研究分成三個部份：首先為nano copper-resin之製備，其次為nano copper-resin的表面分析及最後的nano copper-resin與溶液中六價鉻的批次實驗。利用SEM、和BET觀察nano copper-reson的表面，與利用AAS和UV-Vis測量溶液中總鉻、總銅及六價鉻的濃度。並藉由批次反應實驗，探討不同比例的陽離子交換樹脂與奈米零價銅，對去除溶液中六價鉻與總鉻之影響。 實驗結果顯示，不同比例的陽離子交換樹脂與奈米零價銅具有不同的比表面積，因此其還原六價鉻的能力也不同。在本研究中設定45、35、25、15、5和1 mg-copper/g-resin六種比例的nano copper-resin，在每個批次實驗加入2 g的 nano copper-resin於230mL含有20mg-Cr(Ⅵ)/L的溶液中，實驗發現25 mg/g為去除溶液中六價鉻之最佳比例，經24小時反應後，溶液中六價鉻去除率可以達99%，且銅離子殘留濃度為最低；根據三中pH之影響實驗結果顯示，pH為3之去除率較pH 為 5與7兩者為佳。 將使用過的nano copper-resin，經過氣相還原程序再生後，再進行批次實驗反應，經24小時反應後，六價鉻Cr(Ⅵ)之去除效果仍可達到99%，且對於反應後之Cu2+與三Cr3+仍具良好的回收效果。The objective of this research is to use nanoscale zero valent copper supported on cation exchange resin (nano copper-resin) to reduce hexavalent chromium to trivalent chromium. Using cation exchange resin as the agent of dispersion could disperse nanoscale zero valent copper. In addition, cation resin could recycle divalent copper (Cu2+) and trivalent chromium (Cr3+). There are three major parts in the experiment part. First one is the fabrication of nanoscale copper-resin, second one is nanoscale copper-resin surface analysis, and last one is batch experiment of hexavalent chromium reduction . The characterizations of nanoscale copper-resin surface were investigated by SEM and AAS. The effect of specific surface area of nanoscale copper-resin on reduction of hexavalent chromium were investigated and discussed. Different copper/resin ratios have different specific area and ability to reduce hexavalent chromium. Six Different copper/resin ratios,45, 35, 25, 15, 5, and 1 mg-copper/g-resin was investigated in this study. In each batch experiment, 2 g nanoscale copper-resin were added in 230 mL solution containing 20 mg-Cr(VI)/L. Nanoscale copper-resin in 25 mg-copper/g-resin is the best one to reduce hexavalent chromium. The efficiency for reducing is around 100% in 25 mg-copper/g-resin nanoscale copper-resin after 24 hours. The removal efficiency when pH is at 3 is better than when pH is at 5 and 7. The used nano copper-resin can be regenerated by the reduce process. The regenerated nano copper-resin still had good performance in removal total chromium and hexavalent chromium. Furthermore, had good performance in recycling divalent copper ion and trivalent chromium ion