Abstract |
The objective of the study was to prepare a chemically treated vermiculite with a high phosphate capacity that could be economically regenerated. Many aluminum vermiculites were prepared and tested for phosphate removal. 10 mg PO4/gram of treated vermiculites was the maximum capacity obtained. Highest phosphate capacities were obtained with materials prepared at relatively low pH (3.0) and dilute aluminum solutions (0.1-0.05M). Experimental results showed hydroxylated aluminum vermiculite is inactive towards phosphate ion. The mole ratio of phosphate adsorbed to exchanged aluminum seemed to approach 0.33, or an exchange capacity of 13.7 mg PO4/gm. The most successful regeneration scheme was one in which a dilute sulfuric acid solution containing a small amount of Al2(SO4)3 was used as a regenerant. No significant differences in capacity were found between thermally and chemically exfoliated vermiculite. Vermiculites containing cations other than Al were also prepared. These included Fe(III), Fe(II), La(III), and Cu(II). None appeared more promising than Al-vermiculite. The adsorption isotherm of aluminum-vermiculite was obtained, and the data were found to fit both the Langmuir and Freundlich plots.(WRSIC abstract) |