案，本研究五種含鈀廢液中以E 廠回收率最大，推測為COD 值較小，
溶液中以單純置換反應存在，顯示pH 值範圍1~3.5 為最佳，加藥量
還原劑(鋅、硼氫化鈉、二甲基胺硼烷)在0.5 hr 即達到85%以上之反
應，而隨時間的增加有回溶現象造成，故以0.5 hr 為最佳反應時間。
XRD 分析，以A、E 廠之活化鈀廢液並以鋅置換還原法，所得之
經SEM 分析得知，以鋅為還原劑時回收鈀粉粒徑4~10 μm，以
雖硼氫化鈉之還原力較強，但若以回收的角度而言仍以鋅粉為較佳。;Most of the wastes from the PCB manufacturing processes are copper-containing waste liquids. Due to the waste cleaning method and the consideration of industrial production operating costs in high-concentration portions most of the high-concentration waste solutions are shipped to contractors and recovered. The low-concentration noble metal palladium waste is directly discharged into the wastewater treatment plant. The main purpose of this study is to explore a cost-effective way to recover the precious metal palladium from the low-concentration waste liquid.
The results of the study show that the use of different types of reducing agents for the reduction and recovery of palladium-containing wastes from PCBs are based on the laboratory and actual plant operating results with the cost of reagents, reaction time, pH, deposition type, and recycled palladium content. In order to evaluate the conditions, zinc powder is the best feasible solution. In this study, the recoveries of E-plants in the five Pd-bearing waste liquids are the largest. It is estimated that the COD value is small, and the solution only exists as a single substitution reaction, indicating a pH range of 1~ 3.5 is the best.The more dosing the higher the palladium recovery rate. The best dosage of zinc is 6~7 g/l, and the best recovery rate can be obtained. In the tin-palladium system, due to the tin ion competition, the recovery rate is low resulting in more zinc and copper loss in the waste liquid. Recovery of palladium-containing waste liquor with zinc as a reducing agent, the reaction rate increased with the initial concentration. This reaction follows the Nernst equation reaction, the higher the initial concentration of reduced material, the greater the chemical driving force (ΔE). In different reaction time experiments, it shows that the three reducing agents (zinc, sodium borohydride, dimethylamineborane) reach a reaction of more than 85% at 0.5 hr, but it is caused by the back dissolution phenomenon with time. pH 0.5 is the best reaction time.
XRD analysis is performed on activated palladium wastes of A and E plants and zinc reduction method. The powder is analyzed by XRD and the result of the alignment is palladium. The powder is digested with aqua regia and refluxed and determined by atomic absorption spectrometry (AA). The palladium content is 49.2% and 52.7%, which is the highest recovery content of the reducing agent selected for this study.
According to SEM analysis, the recoverable palladium particle size is 4-10 μm when zinc is used as a reducing agent. And the particle size is 70-100 nm with sodium borohydride, and the particle size is 0.5-2 μm with sodium hypophosphite, Dimethylaminoborane. The particle size obtained by the alkane is 50~70 nm. It can be seen that the dimethylamine borane can get smaller particle size, but it is not good for the recovery of palladium metal from the actual plant., The recovery rate is reduced, while zinc and sodium borohydride are decreased. Flocculated palladium sludge can be obtained to increase filtration efficiency. ASAP surface pore analysis shows that the specific surface area and the smaller porosity can be obtained with sodium borohydride as a reducing agent. Although the sodium borohydride has a stronger reducing power, it is still a zinc powder if it is better recycled.