title: Recovery of hazardous semiconductor-industry sludge as a useful resource.
abstract: Sludge, a solid waste recovered from wastewater of semiconductor-industries composes of agglomerates of nano-particles like SiO(2) and CaF(2). This sludge deflocculates in acidic and alkaline aqueous solutions into nano-particles smaller than 100 nm. Thus, this sludge is potentially hazardous to water resources when improperly dumped. It can cause considerable air-pollution when fed into rotary-kilns as a raw material for cement production. In this study, dried and pulverized sludge was used to replace 5-20 wt.% Portland cement in cement mortar. The compressive strength of the modified mortar was higher than that of plain cement mortar after curing for 3 days and more. In particular, the strength of mortar with 10 wt.% substitution improved by 25-35% after curing for 7-90 days. TCLP studies reveal no detectable release of heavy metals. Preliminary studies showed that nano-particles deflocculated from the sludge, when cured for up to 3 days retain in the modified mortar their nano-size, which become large-sized hydration compounds that contribute to the final mortar strength. Semiconductor sludge can thus be utilized as a useful resource to replace portion of cement in cement mortar, thereby avoiding their potential hazard on the environment.
authors.affiliation: Department of Civil and Disaster Prevention Engineering, National United University, MiaoLi, Taiwan, ROC.
authors.forename: Tzen-Chin
authors.initials: TC
authors.lastname: Lee
authors.forename: Feng-Jiin
authors.initials: FJ
authors.lastname: Liu
mesh_terms: D002124:Calcium Fluoride; D003247:Conservation of Natural Resources; D003252:Construction Materials; D007220:Industrial Waste / Q000517:prevention & control*; D012666:Semiconductors; D012722:Sewage; D012822:Silicon Dioxide
chemical_list: D007220:Industrial Waste; D012722:Sewage; D012822:Silicon Dioxide; D002124:Calcium Fluoride