Selective green removal of arsenic from wet-process phosphoric acid using marine-derived Neptune ball Fibres

Abstract Phosphoric acid is the second most widely produced mineral acid worldwide and is predominantly manufactured via the wet process. However, wet-process phosphoric acid (WPPA) contains significant levels of dissolved and suspended impurities, including toxic heavy metals such as As(V), which lower WPPA quality and pose serious environmental and health risks. Therefore, the development of cost-effective and sustainable purification strategies is of considerable industrial importance. In this study, acid-activated Neptune ball Fibres (ANB3), a marine-derived biomass material, were evaluated as a green and low-cost adsorbent for selective arsenic removal from WPPA. The influence of operational parameters—including initial arsenic concentration, contact time, temperature, and adsorbent dosage—was investigated. Adsorption kinetics followed a pseudo-second-order model, while equilibrium data were best described by the Freundlich isotherm, suggesting heterogeneous multilayer-surface adsorption. Regeneration using 6% acetic acid over three successive washing cycles resulted in 64.5% As desorption, while 35.5% remained strongly associated with the Fibres. Importantly, arsenic removal was achieved with less than 1% P 2 O 5 loss. Under optimized conditions, arsenic removal efficiencies of 80–90% were achieved with negligible P 2 O 5 loss, confirming high selectivity toward arsenic species. Structural and surface characterization of ANB3 before and after adsorption using X-ray diffraction (XRD), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDX), and Fourier-transform infrared spectroscopy (FT-IR) verified arsenic binding onto the Fibre matrix and inorganic constituents, indicating a probable adsorption and possible co-precipitation mechanism. These findings demonstrate that marine-derived Fibres represent a promising, sustainable, and economically viable approach for arsenic removal in wet-process phosphoric acid, supporting cleaner fertilizer production and environmentally responsible acid processing.