A novel lanthanum-modified bentonite, Phoslock, for phosphate removal from wastewaters

Phoslock (R), a lanthanum-modified bentonite, has been investigated for phosphate uptake from synthetic and real wastewaters in laboratory and field. In laboratory tests, equilibrium and kinetics were studied at various temperatures, ionic strength, and pHs. The investigation indicated that phosphate adsorption occurs through a chemisorption process. The activation energy of the adsorption process was calculated based on pseudo-second order rate constant. The maximum adsorption capacity of Phoslock was unaffected at pH 5-7, but decreased at higher pHs. The monovalent phosphate anion, H(2)PO(4)(-), had the greatest affinity for the adsorbent surface. Furthermore, it was also shown that the activation energy was lower at a higher solution pH attributed to the loss of adsorption sites at the higher pHs while it remained unaffected by the ionic strength of the solution. A field test also demonstrated that the Phoslock works well for phosphate uptake in polluted waters. (C) 2009 Elsevier B.V. All rights reserved.