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

Abstract

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. TheCaCl2 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 (R2) 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.

Fixed-Bed Column Technique for the Removal of Phosphate from Water Using Leftover Coal

“…Empty bed contact time (EBCT) is the time of contact between the water phase and the adsorbent (Equation (6)), and it measures critical depth and contact time for the adsorbent [ 23 ]. where V b is adsorbent bed volume (mL), which can be described as ( , H b is the corresponding bed height in cm, r is the inner radius of the bed column tube), and Q is volumetric flow rate (mL/min).…”

“…Adsorption has received immense interest due to its high removal efficiency, simple operation, better cost effectiveness, less or no sludge production, and invulnerability to coexisting pollutants [ 18 , 19 , 20 ]. The application of low-cost and locally available materials for phosphate removal was widely investigated during this decade, such as with modified biochar [ 20 ], steel slag [ 21 ], volcanic rock [ 22 ], alkaline Tunisian soil [ 23 ], chitosan composite [ 24 ], alum sludge [ 25 ], and furnace slags [ 26 ].…”