Removal of Organics and Heavy Metals from Wastewater by Supercritical Carbon Dioxide Extraction

• Main Authors: Chih-Hung Lin, 林志鴻
• Other Authors: Jya-Jyun Yu
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/s4vwv7

碩士 === 逢甲大學 === 環境工程與科學所 === 90 === With the improvement of industrial technology, the composition of wastewater from electroplating plants is getting complex and complex. The chemical precipitation is a conventional technique to remove heavy metal ions from wastewater, but finally sludge must be disposed further. So it must be develop an innovative technique to separate heavy metals from aqueous phase. Due to non-toxic, resource rich and easy separation of extraction solvent, supercritical fluid extraction (SFE) has become an attractive technique to recovery heavy metals from environmental wastewater. However, direct extraction of metal ions from wastewater is impossible because of the charge neutralization requirement. When chelating agent is added, the metal-chelate complex will form and it can be dissolved in supercritical fluid carbon dioxide (SF-CO2). This study is to remove or separate metal ions from aqueous solution and organics from organic wastewater and sewage. First, a chelating agent Acetylacetone(ACAC) was used to chelate with two metal ions (Cr6+ and Be2+) followed by SF-CO2 extraction. The extraction efficiency were studied by batch type apparatus in the pressure and temperature ranges of 170~306atm and 50~90℃. The extraction efficiency of different metal ions as a function of pH, modifier addition, temperature and pressure with supercritical carbon dioxide were measured. More than 85% of metals in the aqueous solution were removed. The results indicated that methanol was added, the quantity of metal-chelate complex dissolve in SF-CO2 is more. So the extraction efficiency is better. Secondary, removal of organics, NH3-N and PO43--P from organic wastewater and sewage. The extraction efficiency of different organics and inorganics as a function of initial concentration, modifier addition, temperature and pressure with supercritical carbon dioxide were measured. More than 80% organics in organic wastewater were removed. Chemical oxygen demand (COD) can achieve in the standard of government. Sewage that treated by secondary treatment process, the extraction efficiency of NH3-N and PO43--P is about 56% and 70%.