Phosphorus removal from wastewater using eggshell ash.

Eggshell ash was used as an adsorbent to remove phosphorus from wastewater. Adsorbent dose, initial phosphorus concentration, and contact time were investigated to determine the optimum conditions. Results indicate that 5 g of eggshell ash adsorbent with 1.5 mg L-1 of initial phosphorus concentration removed over 90% of the phosphorus. When the temperature was increased, phosphorus removal potential also increased. Specific surface area, morphological features, and structure of the adsorbent were characterized by Brunauer-Emmett-Teller (BET) surface area analysis, scanning electron microscopy with energy dispersive X-ray spectrometer (SEM-EDS), and X-ray diffraction (XRD). Results showed prominent calcium, magnesium, and phosphorus in the eggshell ash surface after adsorption. The elemental composition of eggshell ash surfaces before adsorption did not contain phosphorus, revealing that calcium carbonate-based eggshell ash was co-precipitated with calcium phosphate. The adsorption mechanism was studied by applying Langmuir and Freundlich isotherm models. Experimental data fit well with the Langmuir model, which indicates monolayer adsorption. Eggshell ash was also applied as an adsorbent in wastewater at Srinakharinwirot University dormitories, resulting in 80% phosphorus removal within 2 h. These findings indicated that eggshell ash could be applied as an adsorbent for phosphorus treatment and removal from domestic and industrial wastewater.