Journal
ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH
Volume 28, Issue 13, Pages 16282-16297Publisher
SPRINGER HEIDELBERG
DOI: 10.1007/s11356-020-12180-2
Keywords
Excess activated sludge; Biochar; Phosphate; Adsorption; Mechanism; Environmental risk
Categories
Funding
- Doctoral Foundation of University of Jinan [XBS1920]
- National Key Research and Development Program of China [2017YFD0800601]
- Natural Science Foundation of Shandong Province, China [ZR2018MEE007]
Ask authors/readers for more resources
Mg-modified sludge biochar exhibited higher phosphate adsorption capacity and the main mechanisms for phosphate removal included electrostatic attraction, surface complexation, and precipitation, but there is a risk of releasing high amounts of magnesium during practical application.
In this study, Mg-modified sludge biochar (MB) and Mg-Fe double oxides/sludge biochar composites (MFB) were synthesized for enhanced removal of phosphate from aqueous solution. The phosphate adsorption followed the Langmuir-Freundlich isotherm model, and the maximum capacity was 142.31 mg P/g and 35.41 mg P/g for MB and MFB, respectively. MB exhibited the higher adsorption capacity at pH 8-9 and performed well under the influences of coexisting anions and temperature (4-45 degrees C). Adsorption kinetics was well described by the pseudo-second-order kinetic model, indicating the chemical bonding between phosphate and adsorption sites. The adsorption capacity of phosphate decreased by < 15% after three successive recycles. Based on FTIR, XRD, and XPS analysis, the main mechanisms for phosphate removal by MB included electrostatic attraction, surface complexation, and precipitation. Hydroxides/oxides particles of Mg on the surface of MB with positive charge could adsorb HPO42- and PO43- to form surface complex and convert to MgHPO4 and Mg-3(PO4)(2). The released amounts of Fe, Cd, Cr, Pb, Cu, Zn, Sb, and As from MB and MFB were low and acceptable. However, the released amount of Mg was as high as 4.9 wt% for MB and 8.7 wt% for MFB at the pH corresponding maximum adsorption capacity, posing a risk of salt increase. The grass (Lolium perenne L.) germination and early growth with the addition of P-laden biochars as fertilizer are seriously inhibited due to the high alkalinity, particularly for MB. The environmental risk of P-laden biochars (with high alkalinity and salt content) as fertilizer should be emphasized in practical application.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available