Removal performance of phosphate from aqueous solution using a high-capacity sewage sludge-based adsorbent

Abstract

Excessive phosphate always leads to eutrophication in water bodies, which has been paid much attention in recent years. In this work, sewage sludge derived adsorbent was used to remove phosphate from aqueous solutions with the activation of ZnSO4·7H2O and H2SO4. The suitable dosages of the activation agents with the production of the carbonized sludge were determined. The adsorption performance was evaluated with different initial phosphate concentrations. The kinetics and isotherms were also discussed. Adsorbent characterization was studied by some analysis methods such as X-ray diffraction (XRD) and FTIR to understand the adsorption mechanism. In addition, the effects of pH, temperature, and adsorbent dosage on phosphate removal were investigated. The maximum phosphate adsorption capacity of the adsorbent was 123.46 mg g−1. The sorption kinetic data had excellent fitness of the pseudo-second-order equation, indicating that the removal process belonged to chemisorption. Under the optimal condition (pH 5.0, temperature 35 °C, adsorbent 0.15 g), more than 99% of 65 mg l−1 initial phosphate were removed within 0.5 h. The results suggested that ZnSO4·7H2O and H2SO4 enhanced the phosphate adsorption and the adsorbent had the potential to remove phosphate effectively from aqueous solutions.