Hydroxyl-eggshell: a novel eggshell byproduct highly effective to recover phosphorus from aqueous solutions

Abstract

Efficient recovery and reuse systems are an ever-increasing challenge for global phosphorus security. This work presents a standard and straightforward methodology to produce a novel eggshell byproduct with a high P-recovery capacity. The material was obtained from chicken eggshells after reaction with hydrochloric acid and sodium hydroxide solutions and named as Hydroxyl-Eggshell (ES-OH). Batch experiments were conducted to investigate the effects of ES-OH doses, contact time, and initial P concentration on the recovery process. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDS), and X-ray diffraction (XRD) were used to characterize the material before and after P reaction. The kinetics study showed that the pseudo-second-order model described well the process. The maximum P recovery capacity was 328.9 mg g−1, which is higher than that found for other materials derived from eggshells. FTIR, SEM-EDS, and XRD confirmed that the primary process of P recovered by ES-OH is via precipitation as hydroxyapatite. Finally, a pot experiment confirmed that the P-loaded ES-OH was as effective as triple superphosphate (TSP) on grass yield with the advantage of maintaining nearly four-fold more available P and higher soil pH than TSP after cultivation. The results presented in this work showed that ES-OH is a promising material for P recovery from aqueous solution, forming a material with great potential to be used in agriculture as an alternative phosphate fertilizer.