Effect of pre-treatment of bentonite with sodium and calcium ions on phosphate adsorption onto zirconium-modified bentonite

• Published in: Journal of environmental management Vol. 217; pp. 183 - 195
• Main Authors: Lin, Jianwei, Jiang, Bohui, Zhan, Yanhui
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-07-2018
• Subjects: Adsorption; Bentonite; Calcium; Hydrogen-Ion Concentration; Kinetics; Phosphate; Phosphates - isolation & purification; Pre-treatment of bentonite with calcium ion; Pre-treatment of bentonite with sodium ion; Sodium; Water Pollutants, Chemical - isolation & purification; Water treatment; Zirconium; Zirconium-modified bentonite; Water treatment; Zirconium-modified bentonite; Pre-treatment of bentonite with sodium ion; Pre-treatment of bentonite with calcium ion; Adsorption; Phosphate
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2018.03.079

To understand the influence of the pre-treatment of bentonite with Na+ and Ca2+ on the adsorption of phosphate on zirconium-modified bentonite, three kinds of adsorbent materials including zirconium-modified raw, Na+-pretreated and Ca2+-pretreated bentonites were synthesized and characterized firstly, and afterward their adsorption performance and mechanism for phosphate were studied comparatively. The phosphate adsorption ability for zirconium-modified bentonite decreased after the pre-treatment of bentonite with Na+, but it increased after the pre-treatment of bentonite with Ca2+. The maximum phosphate adsorption capacity calculated from the Langmuir isotherm model for zirconium-modified Ca2+-pretreated bentonites (13.4 mg P/g) was much higher than that for the zirconium-modified raw bentonite (9.06 mg P/g). The pre-treatment of bentonite with Na+ and Ca2+ did not change the interaction type between zirconium-modified bentonite and phosphate, i.e., the coordination of phosphate to zirconium. The decreased phosphate adsorption capacity for zirconium-modified bentonite induced by the Na+ pre-treatment could be mainly attributed to the decrease of the specific surface area and the content of exchangeable Ca. The increased phosphate adsorption capacity for zirconium-modified bentonite induced by the Ca2+ pre-treatment could be mainly due to the increase in the amount of exchangeable Ca. Results of this work suggest that the zirconium-modified Ca2+-pretreated bentonite is more suitably used as an adsorbent for the removal of phosphate from wastewater than the zirconium-modified raw and Na+-pretreated bentonites.
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•Zr was used to modify bentonite (BT), and Zr-modified BT (ZrBT) was prepared.•Pre-treatment of BT with Na decreases Ca and specific surface area (SSA) of ZrBT.•Na pre-treatment reduces P sorption due to decrease in Ca content and SSA of ZrBT.•Pre-treatment of BT with Ca increases Ca amount but has no effect on SSA.•Ca pre-treatment enhances P sorption because of increase in Ca amount of ZrBT.