title: Influence of calcination on the adsorptive removal of phosphate by Zn-Al layered double hydroxides from excess sludge liquor.
abstract: The influence of calcination of Zn-Al layered double hydroxides (LDHs) on their phosphate adsorption capacity was studied in order to improve phosphorus removal from an excess sludge liquor. Powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), thermogravimetry-differential scanning calorimetry (TG-DSC) and nitrogen adsorption-desorption were employed to characterize the raw Zn-Al and the calcined products. The results reveal that the Zn-Al LDHs evolved to a phase of mixed metal oxides with the calcination temperature increasing to 300 degrees C and finally to spinel ZnAl(2)O(4) at 600 degrees C. When the Zn-Al was calcined at 300 degrees C, the interlayer carbonate ions were removed and the greatest BET surface area of 81.20 m(2)/g was achieved. The tested phosphate adsorption capacities of the raw and calcined Zn-Al were closely related to the evolution of physicochemical properties of the LDHs during the calcination. The Zn-Al-300 (Zn-Al LDHs calcined at 300 degrees C) exhibited the highest P uptake of 41.26 mg P/g in 24h. The phosphate adsorption by the raw Zn-Al and the Zn-Al-300 both follows a pseudo-second-order kinetic model; the adsorption isotherms show a good fit with a Langmuir-type equation.
authors.affiliation: School of Municipal & Environmental Engineering, Harbin Institute of Technology, 202 Haihe Road, 150090 Harbin, China. sean.d.cheng@gmail.com
authors.forename: Xiang
authors.initials: X
authors.lastname: Cheng
authors.forename: Xinrui
authors.initials: X
authors.lastname: Huang
authors.forename: Xingzu
authors.initials: X
authors.lastname: Wang
authors.forename: Dezhi
authors.initials: D
authors.lastname: Sun
mesh_terms: D000327:Adsorption; D000535:Aluminum; D006878:Hydroxides / Q000737:chemistry*; D007700:Kinetics; D010710:Phosphates / Q000302:isolation & purification*; D012722:Sewage; D018505:Waste Management / Q000379:methods*; D015032:Zinc
chemical_list: D006878:Hydroxides; D010710:Phosphates; D012722:Sewage; D000535:Aluminum; D015032:Zinc