Characterization of carbonated tricalcium silicate and its sorption capacity for heavy metals: A micron-scale composite adsorbent of active silicate gel and calcite

• Published in: Journal of hazardous materials Vol. 153; no. 1; pp. 775 - 783
• Main Authors: Chen, Quanyuan, Hills, Colin D., Yuan, Menghong, Liu, Huanhuan, Tyrer, Mark
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.05.2008; Elsevier
• Subjects: Adsorbent; Adsorption; Adsorption capacity; Applied sciences; Calcium Carbonate - chemistry; Calcium Compounds - chemistry; Carbon - chemistry; Chemical engineering; Exact sciences and technology; General purification processes; Heavy metal; Metals, Heavy - chemistry; Pollution; Silica Gel; Silicates - chemistry; Silicon Dioxide - chemistry; Tricalcium silicate (C 3S); Waste Disposal, Fluid - methods; Wastewater; Wastewaters; Water Pollutants, Chemical - chemistry; Water Purification - methods; Water treatment and pollution; Adsorption capacity; Adsorbent; Wastewater; Tricalcium silicate (C 3S); Heavy metal; Scanning electron microscopy; Adsorption isotherm; Metal ion; Differential thermal analysis; Nitrates; Retention; Composite material; Waste water; Sorption; Adsorption; Batchwise; Industrial waste water; Preparation; Tricalcium silicate (C3S); Lead; pH; Carbonation; Silica gel; Kinetics
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2007.09.023

Adsorption-based processes are widely used in the treatment of dilute metal-bearing wastewaters. The development of versatile, low-cost adsorbents is the subject of continuing interest. This paper examines the preparation, characterization and performance of a micro-scale composite adsorbent composed of silica gel (15.9 w/w%), calcium silicate hydrate gel (8.2 w/w%) and calcite (75.9 w/w%), produced by the accelerated carbonation of tricalcium silicate (C 3S, Ca 3SiO 5). The Ca/Si ratio of calcium silicate hydrate gel (C–S–H) was determined at 0.12 (DTA/TG), 0.17 ( 29Si solid-state MAS/NMR) and 0.18 (SEM/EDS). The metals-retention capacity for selected Cu(II), Pb(II), Zn(II) and Cr(III) was determined by batch and column sorption experiments utilizing nitrate solutions. The effects of metal ion concentration, pH and contact time on binding ability was investigated by kinetic and equilibrium adsorption isotherm studies. The adsorption capacity for Pb(II), Cr(III), Zn(II) and Cu(II) was found to be 94.4 mg/g, 83.0 mg/g, 52.1 mg/g and 31.4 mg/g, respectively. It is concluded that the composite adsorbent has considerable potential for the treatment of industrial wastewater containing heavy metals.