4.5 Article

Adsorption of phosphorus by alkaline Tunisian soil in a fixed bed column

Journal

WATER SCIENCE AND TECHNOLOGY
Volume 78, Issue 4, Pages 751-763

Publisher

IWA PUBLISHING
DOI: 10.2166/wst.2018.341

Keywords

adsorption; breakthrough curve; modeling; phosphorus; salts; soil

Funding

  1. laboratory of Energy and Materials
  2. FP7 FP4BATIW

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The present study evaluates the phosphorus (P) adsorption by alkaline soil in fixed bed column mode operation. The effects of flow rate, bed height, and initial P concentration on breakthrough curves were evaluated. Data confirmed that both the breakthrough and exhaustion time increased in parallel with the rise in bed height and the decline in flow rate and initial P concentration. The adsorption capacity was observed to increase with decreasing flow rate and bed height and increasing initial concentration. Moreover, continuous adsorption experiments were conducted using three salts (NaCl, KCl and CaCl2) with the same concentration (0.01 M) to investigate the P adsorption behavior in saline conditions. The results showed that all three salts improve the P adsorption in the soil column. Consequently, the bed performance was significantly enhanced with salts addition. The maximum adsorption capacity of 13.47 mg g(-1) for P, 16.13 mg g(-1) for P-NaCl, 22.10 mg g(-1) for P-KCl, 30.05 mg g(-1) for P-CaCl2 was attained at an initial influent concentration of 300 mg g(-1), bed height of 22 cm, and flow rate of 10 mL min(-1). TheCaCl(2) addition was therefore the most effective in increasing P adsorption. Thomas, Yoon-Nelson and Clark models were applied to experimental results to forecast the breakthrough curves by nonlinear regression analysis. Meanwhile, the bed depth service time model was employed to examine the effective model parameters in scaling up the process using linear regression analysis. The values of correlation coefficient (R-2) and the sum of squared error evidenced that the Thomas model is the most appropriate model to fit the experimental data. The reusability experiment showed that the adsorbent material still had high P adsorption capacity, and tolerable desorption efficiency.

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