Phosphate Removal from Water and Wastewater using Sepia (Cuttlefish) Endoskeleton Powder as a Natural Adsorbent

Abstract

Wastewaters produced from various industries and their entry into surface water is one of the most important environmental problems that have harmful effects on aquatic life. Discharging phosphate from urban and industrial wastewater to the aquatic environment causes a lot of algae growth. The aim of this study was to evaluate the removal of phosphate from aqueous solutions using sepia endoskeleton (cuttlebone) powder as a natural biomass, cheap and non-toxic absorbent. This study was conducted in a batch system. Sepia endoskeleton was washed with distilled water. It was then dried at 80 °C and thoroughly powdered by milling. Physical and chemical properties of the adsorbent were determined using the Particle Sizer, atomic force microscopy, and infrared spectroscopy and X-ray fluorescence. The effects of variables affecting phosphate uptake, such as pH, adsorbent amount, contact time, initial concentration of phosphate and stirring rate were optimized. Also, the isotherm models (Langmuir, Freundlich, Tamkin and Dubbin-Radshkvich) and first-order and second-order kinetics models were used to evaluate the data. The results showed that the highest removal percentage was observed at pH 5, adsorbent content of 5 g/L and contact time of 10 min at initial phosphate concentration of 10 mg/L. Using sepia powder under optimal laboratory conditions, the phosphate ion with the concentration of 10 mg/L was removed with a yield of over 99%. The results indicated that the Freundlich isotherm model gives a better description than other models showing the adsorption of phosphate ions occurs in a heterogeneous surface. Using Langmuir model, the maximum absorption capacity for phosphate was 68.02 mg/g. The kinetic model of phosphate removal followed the pseudo-second-order model. Besides, the percentage of removal of the real samples was over 98%, indicating the great ability of this natural and inexpensive absorbent to remove this pollutant from the water solutions.