Contents lists available at ScienceDirect Journal of Environmental Management journal homepage: www.elsevier.com/locate/jenvman Research article Dolomite used in phosphate water treatment: Desorption processes, recovery, reuse and final disposition M. Natalia Piol a,* , María Paricoto a , Andrea B. Saralegui a , Silvana Basack b , Diana Vullo b,c , Susana P. Boeykens a a Universidad de Buenos Aires, Facultad de Ingeniería, Laboratorio de Química de Sistemas Heterogéneos (LaQuíSiHe), Paseo Colón 850, 5to piso (C1063ACU), Buenos Aires, Argentina b Universidad de General Sarmiento, Instituto de Ciencias, J.M. Gutiérrez, 1150, Los Polvorines, (1613) Buenos Aires, Argentina c CONICET, Godoy Cruz 2290 (C1425FQB), CABA, Argentina ARTICLE INFO Keywords: Desorption Phosphate Dolomite Final disposal Phosphate-solubilizing microorganisms ABSTRACT Desorption is a method that contributes to two important aspects for the sustainability of the water treatments that involve adsorption processes: a) the regeneration of the adsorbent making it reusable in several efficient cycles and, b) the recovery of the adsorbate. In previous studies, it was shown that dolomite constituted an efficient adsorbent of phosphates from aqueous solutions. Once the adsorbent saturation is achieved, it becomes useless for further uses, generating waste, a new environmental problem if it could not be properly disposed. In this work, the main objectives were to study the phosphate desorption process for the recovery and reuse of dolomite and to evaluate the possibilities of a final disposal of exhausted dolomite for agricultural soil im- provement and applying the desorbed phosphate as fertilizer. The most efficient agent for the desorption process was 1 M NH 4 Cl. Ultrasound evidenced a negative effect on desorption. The pseudo-second order model fitted better the experimental data and the equilibrium time was 30 min. Up to four efficient adsorption-desorption cycles were obtained. Phosphate bioavailability of exhausted dolomite was assessed with autochthonous mi- croorganisms. The obtained extracts were used in Lactuca sativa growth experiments, establishing that they are not phytotoxic and otherwise, could promote the vegetal growth. 1. Introduction Phosphorus is not only an essential macronutrient of living organ- isms, it is also one of the main environmental concerns because it could cause the excessive proliferation of algae and other aquatic plants in what is called the eutrophication process (Manahan, 2001). Although phosphorus is found naturally in surface waters, certain human activ- ities contribute significantly to its accumulation, causing the dete- rioration of the water body as consequence of the depletion of oxygen, the loss of aesthetic value and the growth of algal blooms that are capable, in some cases, of producing toxins harmful to health (Ashekuzzaman and Jiang, 2014). If these algal blooms occur in water bodies destined as sources of drinking water, recreation or baths, they could cause important damages from the sanitary point of view (Falconer, 1996). There is a growing need for development of processes to minimize the phosphorus release to the environment. Within the new technolo- gies, the adsorptive processes present a great potential to reduce phosphate concentration at a trace level, due to its low cost, easy procedure, versatility and possibility of reusing the adsorbent (Dabrowski, 2001). Some mesoporous and modified materials (Huang et al., 2017), minerals (Coulibaly et al., 2016) and oxides and hydro- xides of many polyvalent metals (Johir et al., 2016) were investigated for their capacities to adsorb phosphate. In our previous studies, it was shown that a low cost material, dolomite (a sedimentary rock composed mainly of calcium and magnesium carbonates), is an efficient adsorbent of phosphate from aqueous solutions containing other contaminants (Boeykens et al., 2017). Once the adsorbent has become saturated with the contaminant, it can be considered as a waste, generating a new environmental problem if it is not properly disposed (Han et al., 2009). This problem can be overcome through the use of new post-treatment and disposal meth- odologies. Desorption is a method that provides two important aspects for the sustainability of the treatment process: a) the regeneration of the adsorbent making it reusable in several efficient adsorption/desorption cycles and, b) the isolation and recovery of the adsorbate. The https://doi.org/10.1016/j.jenvman.2019.02.085 Received 12 October 2018; Received in revised form 6 February 2019; Accepted 17 February 2019 * Corresponding author. E-mail addresses: natypiol@yahoo.com.ar, laquisihe@fi.uba.ar (M.N. Piol). Journal of Environmental Management 237 (2019) 359–364 0301-4797/ © 2019 Published by Elsevier Ltd. T