Recycling of phosphorus from aqueous solutions by pine needles

Abstract

In this study, it is aimed to use phosphate ions in aqueous solution for production of phosphated organic fertilizers by using pine needles. Pine needles (PN), pine needles modified by NaOH (Na-MPN), pine needles modified by CH3OH NaOH solutions (MeOH-MPN) were used as adsorbents. Adsorbent amount (0.1-0.3 g/100 mL), contact time (15-1,440 min), pH (3-10), initial concentration (20-150 ppm) and temperature (25 degrees C, 35 degrees C, and 50 degrees C) were the selected parameters. Microstructures, chemical and physical properties of the adsorbents were characterized, respectively, by Fourier transform infrared spectroscopy (PerkinElmer Spectrum 100, USA) and scanning electron microscope (ZEISS Supra 40VP, USA). According to experimental results and analyses, it was shown that lignin compound found in pine needles decreases the phosphate adsorption capacity of pine needles. The pseudo-second-order model for the Na-MPN adsorbent optimally fits the phosphate adsorption kinetics, and the data are coherent with Langmuir and Dubinin-Radushkevich (D-R) adsorption isotherm models. Furthermore, thermodynamic studies show that the adsorption process occurs spontaneously and naturally in an exothermic manner. As a result, it has been determined that it can be used as phosphated organic fertilizer in soils and waters where phosphate is insufficient by adsorbing phosphate ions to pine needles whose lignin were removed from waters having high phosphate concentration.