2.4. Batch Experiment

The stock solution of phosphate (100 mg/L) was prepared by dissolving K₂HPO₄ in water. All batch sorption experiments on phosphate were conducted in triplicate:

To investigate the effect of adsorbent amounts on phosphate adsorption, 0.025, 0.050 and 0.100 g of WBC and WBC1x were added to 25 mL phosphate stock solution in a 50 mL beaker, respectively. The beakers were sealed in plastic wrap and shaken in a temperature-controlled gas bath at 120 rpm and 30 °C, and samples were taken at a preset time;

To study the effect of pH, the pH of the KH₂PO₄ solution was adjusted in a range between 3 and 10 by using 1.00 mol/L NaOH or 1.00 mol/L HNO₃ 0.05 g WBC1x was added to 25 mL adjusted phosphate solution in a 50 mL beaker, respectively. The beakers were sealed in plastic wrap and shaken in a temperature-controlled gas bath at 120 rpm and 30 °C, and samples were taken at preset time;

To investigate the effect of anions (Cl⁻, SO₄²⁻ and Cl⁻ + SO₄²⁻), mixing a series of effective concentrations of anions (50, 100, 150, 200 and 250 mg/L) with 50 mg/L of KH₂PO₄. Then, 0.05 g WBC1x was added to 25 mL adjusted phosphate solution in a 50 mL beaker, respectively. The beakers were sealed in plastic wrap and shaken in a temperature-controlled gas bath at 120 rpm and 30 °C, and samples were taken at preset time;

In the batch sorption experiments, 0.05 g WBC, WBC10, WBC11, and WBC20 were added to 25 mL phosphate stock solution in a 50 mL beaker, respectively. The beakers were sealed in plastic wrap and shaken in a temperature-controlled gas bath at 120 rpm and 30 °C, and samples were taken at preset time;

n the isothermal adsorption experiments, 0.05 g of WBC, WBC10, WBC11, and WBC20 were added to 25 mL KH₂PO₄ solution with a concentration ranging from 5 to 400 mg·L⁻¹, in a 50 mL beaker, respectively. The beakers were sealed in plastic wrap and shaken in a temperature-controlled gas bath at 120 rpm and 30 °C for 12 h, and samples were taken at preset time.