Polymer-treated woody biomass: a filtration medium for removing phosphate from water
A two-stage treatment of refined aspen wood fiber with solutions of carboxymethyl cellulose (CMC) and ferrous chloride afforded a filtration medium that was effective in removing phosphate from test solutions. To assess the stability of the filtration medium, samples exposed to the test solutions were analyzed by FTIR spectroscopy. The resultant spectra indicated that a significant amount of the carboxylate functionality, imparted by the CMC, remained with the fiber. Determinations of iron and phosphorous levels in these samples by elemental analysis confirmed that the CMC provided additional sites to complex iron ions, and that phosphate removed from the test solutions was retained within the filtration medium. To better understand the distribution of the CMC in the fiber matrix, treatments were also carried out with CMC containing a polymeric fluorescent dye. Observations by confocal laser scanning microscopy showed partial filling of the fiber lumens. To address concerns related to the hydraulic conductivity of the fibers, aspen wood particles of different sizes were also treated. Results showed that the phosphorous uptake capacity decreased with decreasing particle size. Measurement of iron released into the test solutions suggested that the smaller wood particles may be preferred since they showed the lowest release of iron relative to the amount of phosphate removed.