Cleaner production of iron-coated quartz sand composites for efficient phosphorus adsorption in sanitary wastewater: A design of experiments (DoE) approach

Abstract

Phosphorus (P) adsorption and recovery from sanitary wastewater is a promising route to produce more sustainable fertilizers. Multivariate Design of Experiments (DoE) techniques were used to develop a cleaner process to produce Fe-coated quartz sand composites with applications in Phosphorus (P) adsorption from sanitary effluents. Nine different process parameters were investigated and correlations between process inputs and physicochemical characteristics of adsorbents were elucidated. It was found that Goethite and Magnetite phases with different degrees of crystallinity were obtained depending on the conditions applied during the synthesis by coprecipitation. Statistical models fitted to an experimental multivariate database were used to predict the best conditions for synthesizing an efficient P adsorbent. In addition, a zero-waste process for the production of the adsorbents is reported. The best adsorbent produced, an aqueous suspension containing particles of a SiO2@FeOOH composite, exhibited a P (KH2PO4) adsorption capacity of 12.4 mg P/g (C0 = 10 mg P/L, pH 6.0) and robust performance when applied in simulated sanitary effluent, reaching 97% of P removal efficiency (C0 = 5 mg P/L). Considering the value of the green star area index (GSAI), the optimized method (suspension) was 65% green, reaching the maximum score for four of the ten principles involved, denoting the greenness of the proposed method. The optimized adsorbent has appropriate characteristics to be applied in sanitary effluent treatment processes for capturing and recovering residual P, contributing to a more sustainable management of natural resources.