Exploratory study to assess the use of lanthanum-modified chitosan as a potential phosphorous adsorbent

ABSTRACT The main objective of this study was to explore the potential of a lanthanum-modified chitosan (LaCt) as a phosphorus adsorbent and to compare its performance in removing phosphorus from waste-water with an aluminum-modified bentonite adsorbent (Al-Bt). The La-Ct adsorbent was initially prepared as a solution containing 112 mg La/g chitosan to which NaOH was added to form La-Ct flakes, which were collected using a mesh then washed, dried, and used for phosphorus removal. The Al-Bt adsorbent was prepared by adding a solution containing hydroxy-aluminum-polycations to bentonite suspended in distilled water. The resulting modified clay was filtered, washed, dried, and ground to a suitable size. The experimental phosphorus adsorption results for both adsorbents fitted well both, the Freundlich and Langmuir adsorption isotherms, with R 2 values above 0.9. The adsorption capacities reached 10.7 mg P/g for the Al-Bt adsorbent and 17.9 mg P/g for the La-Ct adsorbent. The kinetic study showed that the adsorption rates of the two adsorbents were well represented by the pseudo-second-order kinetic model, with adsorption rate constants of 0.00543 and 0.0021 g/(mg min) for the Al-Bt and La-Ct adsorbents, respectively. The study demonstrated that the La-Ct adsorbent was effective for phosphorus removal and significantly more efficient than the Al-Bt adsorbent.