Phosphorus adsorption from aqueous solutions using different types of cement: kinetics, isotherms, and mechanisms
Xingyu Yu1,2,3, Yongqiang Yang1,2, Hanxiao Zhang1,2,3
1CAS Key Laboratory of Mineralogy and Metallogeny, Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences 511 Kehua Street 510640 Guangzhou China yqyang@gig.ac.cn.
Abstract:
Exploring low-cost and high-performance phosphorus (P) adsorbents is key to controlling P contamination in water. This study evaluated the P adsorption performance of three types of cement: Ordinary Portland cement (OPC), Portland slag cement (PSC), and Portland pozzolana cement (PPC). Furthermore, SEM-EDS, XRD, XPS, and FTIR were employed to reveal the adsorption mechanism. The results showed that the pseudo-second-order model exhibited higher regression coefficients than the pseudo-first-order model, indicating that chemisorption dominated the adsorption process. The Langmuir equation fitted the P adsorption data well, with maximum P adsorption capacities of 245.8, 226.1, and 210.0 mg g-1 for OPC, PSC, and PPC at 25 °C, respectively. P adsorption capacities decreased gradually with increasing initial pH and reached their maximum values at pH 3. The anions of F-, CO32-, and SO42- negatively affected P adsorption due to the competitive adsorption with Ca2+. The results of XPS, XRD, and FTIR confirmed that Ca-P precipitates (i.e., hydroxyapatite) were the main removal mechanism. A real domestic sewage experiment showed that 0.6 g L-1 OPC effectively reduced the P concentration from 2.4 to below 0.2 mg L-1, with a dosage cost of 0.034 $ per ton. This study indicated that cement, as a low-cost and efficient P adsorbent, has great potential for application in removing P from acidic and neutral wastewater.
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