Excessive levels of phosphate in stormwater runoff can negatively impact receiving surface water bodies, such as retention ponds, and may also seep into groundwater. Liner systems composed of materials with greater phosphate selectivity have the potential to mitigate infiltration and eliminate phosphate. One potential material is chitosan, an abundant naturally occurring biopolymer. This study evaluated five materials for their ability to remove phosphate from synthetic stormwater using batch tests with different initial phosphate concentrations ranging from 0.5 to 12 mg/L and a fixed 24-h exposure time. The materials included two types of clayey soils (kaolin and bentonite) and three different varieties of chitosan with varying molecular weights (low, medium, and high). The phosphate removal efficiency of kaolin was found to be the highest, with efficiencies ranging from 100% to 56% at different concentrations, while bentonite was found to be the least effective, with removal efficiencies ranging from 40% to 12%. The removal efficiencies of all three types of chitosans analyzed were higher than those of bentonite but lower than those of kaolin. The removal efficiencies ranged from 77% to 19% for low-molecular-weight chitosan, 84% to 31% for medium-molecular-weight chitosan, and 55% to 18% for high-molecular-weight chitosan. The removal mechanism of phosphate by kaolin and bentonite was attributed to surface adsorption and precipitation. In chitosan, the likely mechanism is electrostatic attraction. The maximum adsorption capacity for kaolin was not reached under the tested phosphate concentration range, indicating potential adsorption sites remained available on the particle surfaces. The results for bentonite, low-molecular-weight chitosan, and high-molecular-weight chitosan showed that these materials nearly reached their maximum adsorption capacities, indicating that fewer adsorption sites were remaining. The Langmuir adsorption isotherm was found to be the best-fit model for phosphate adsorption in all the materials tested compared to the Freundlich isotherm. According to the Langmuir model, the maximum adsorption capacities for kaolin, bentonite, low-molecular-weight chitosan, medium-molecular-weight chitosan, and high-molecular-weight chitosan were found to be 140.85, 33, 48.78, 82.64, and 51.28 mg/kg, respectively.
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Phosphate removal using aluminum-doped magnetic nanoparticles
Modern industrial waste waters often contain high concentrations of phosphate, and many methods have been explored to aid in its removal. This study investigates the use of magnetic nanoparticles as an adsorbent for phosphate removal. Aluminum-doped magnetic nanoparticles were synthesized using a co-precipitation method. Structure and composition analysis of the prepared magnetic nanoparticles indicated an inverse spinal structure with a composition of FeAl0.75Fe1.25O4. These nanoparticles were tested for their phosphate removal properties, including adsorption capacity, selectivity, and kinetic models. They showed great affinity to phosphate with a maximum adsorption capacity of 102 mg/g. Additionally, the adsorption was selective, and the presence of other common anions and organic matters did not interfere with the phosphate adsorption efficacy. The kinetic analysis of phosphate adsorption suggested a pseudo-second-order adsorption behavior, and the adsorption isotherm studies indicated a Langmuir type adsorption. The phosphate removal capabilities of the nanoparticles were also tested in poultry rinsing water, tap water, and municipal wastewaters, all with high phosphate removal efficiency. The overall results from these experiments showed promising results for the phosphate removal efficacy of these nanoparticles.
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- Award ID(s):
- 1559087
- PAR ID:
- 10022529
- Date Published:
- Journal Name:
- Desalination and water treatment
- Volume:
- 58
- ISSN:
- 1944-3986
- Page Range / eLocation ID:
- 239–248
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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