Developing multiple physico-chemical technologies to detoxicate chromium from electroplating sludge

• Main Authors: Yu-Chien Lin, 林友千
• Other Authors: none
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/36622693186204121007

碩士 === 國立聯合大學 === 環境與安全衛生工程學系碩士班 === 94 === The quantity of metal containing sludge in Taiwan grew rapidly and most of such sludge was treated by a traditional method―solidification and landfill. However, solidification and landfill have many disadvantages such as space occupation, fragile structure of solidification product by weathering, and leaching potential of metals etc. Therefore, developing innovative detoxification technologies for metal containing sludge is the major purpose of this study. Detection method affecting hazard identification is the first consideration in waste detoxification process and TCLP test is the only regulatory method for hazardous waste identification in most countries. However, TCLP test using acetic acid as an extractant may be influenced by some factors. Another detection method―total content (TC), using nitric acid and hydrogen peroxide for thermo-digestion and reflecting more real pollutant content in waste, was selected to compare with TCLP by an analysis of 500 sets of TCLP and TC data of inorganic sludge. The results showed that r2 of Cd, Cr, Cu, Pb, and Zn between TCLP and TC were 0.0047−0.64 and weak correlations were found. Thus, detections of both TCLP and TC during sludge detoxification process will be included. Most sludge generated from different industrials may contain different metals and concentrations, which could be transported to a co-treatment plant and treated by a same process, even same dosage. Such process often causes TCLP failure since non-uniform constituents in sludge products. An auto-normalization program (Auto-Nor program) had been developed for presorting numerous sludge into several optimal groups. The results of demonstration of 14 industrial metal containing sludge showed that three optimal groups were pre-sorted. Nine sludge in the first optimal group could mix directly without any dosage, indicating that Auto-Nor program is able to provide a cost-saving method for sludge co-treatment. In the second and third optimal groups, the normalized concentrations were predicted and proper dosages for sludge treatment could be conveniently applied. After finishing the above pre-research, we focused on developing multiple physico-chemical detoxification technologies for a Cr-containing electroplating sludge. All detoxification technologies were classified as three phases. Phase-I was “assistant extraction” (including experiment-I and II). Results of phase-I showed that the removals of Cr in the TC detections were nearly 100%, but failed in TCLP detections. Phase-II was “thermo-treatment and then extraction” (including experiment-III and -IV). Although parts of samples passed TCLP regulatory standard, TC removals were very low. Phase-III was “extraction and then thermo-treatment” (including experiment-V, -VI, -VII, -VIII, and -IX). In experiment-VII, -VIII, and -IX, parts of detoxification results showed that TCLP detections of 0.56−1.63 mg/L passed regulatory limit (5 mg/L). In addition, high performance of TC removals of 96.1−99.6% suggested that “extraction and then thermo-treatment” was a nice detoxification process that could remove Cr efficiently from electroplating sludge.