Increasing Soluble Phosphate Species by Treatment of Phosphate Rocks with Acidic Waste

Abstract

The development of efficient fertilizers with a diminished environmental footprint will help meet the increasing demand for food and nutrients by a growing global population. Our objective was to evaluate whether an acidic mine waste (AMW) could be used beneficially by reacting it with sparingly soluble phosphate rocks (PRs) to produce more soluble P fertilizer materials. Three PRs from Brazil and Peru were reacted with different concentrations of AMW. Changes in mineralogy and P species were determined using a combination of X-ray diffraction and phosphorus K-edge XANES spectroscopy, in addition to extractable P concentrations. Increasing the AMW concentration typically increased extractable P. X-ray diffraction data showed transformation of apatite to other species when PRs were reacted with AMW at ≥50% (v/v) in water, with gypsum or anhydrite forming at AMW concentrations as low as 12.5%. Linear combination fitting analysis of X-ray absorption near edge structure spectra also indicated a progressive transformation of apatite to noncrystalline Fe(III)-phosphate and more soluble Ca-phosphates with increasing AMW concentration. Because this AMW is costly to dispose of, reacting it with PR to produce a higher-grade phosphate fertilizer material could decrease the environmental impacts of the AMW and diminish the consumption of pure acids in conventional P fertilizer production.

Acid Ammonium Citrate as P Extractor for Fertilizers of Varying Solubility

“…For P extractability in all used extractors, the acid treatment of Araxá and Patos PRs showed to be effective in increasing the fertilizer quality of their end products (PAPR), especially for water-P, CNA-P, and CA-P (Mattiello et al, 2016;Santos et al, 2016;Barreto et al, 2018), but also for FA_P and AAC_P. This increase in the solubility of PAPR products was due to the transformation of apatite minerals into new P species, supposedly non-crystalline iron and calcium phosphate as well as monocalcium phosphate and dicalcium phosphate, as reported by Santos et al (2016). In addition, the combination of XRD and P extractability data suggests that all PRs were partially solubilized by acid treatment.…”

“…Araxá PR is an apatite concentrate from igneous deposits, while Patos PR is obtained from a sedimentary medium-grade metamorphism Rev Bras Cienc Solo 2019;43:e0180072 deposit; both can be found in the state of Minas Gerais, Brazil. The highly crystalline hydroxyapatites and fluorapatites are the most common P sources in Brazilian phosphates (Santos et al, 2016), considered to be low-reactive fertilizers for direct use (Barreto et al, 2018). In addition, the high occurrence of Fe-, Al-, and Si species in the deposits of these phosphates has prompted the industries to concentrate the apatite minerals prior to the production of P-fertilizers.…”

“…Bayóvar PR is a phosphorite mined in a marine sedimentary deposit in the Sechura Desert in Peru. The phosphate mineral contained in Bayóvar PR is mainly hydroxyapatite of high porosity (Baldoino, 2017) and low crystallinity (Santos et al, 2016).…”

“…Partially acidulated phosphate rocks (PAPRs) are produced by reaction of PRs with an acidic wastewater, as demonstrated by Barreto et al (2018). The wastewater is highly acidic (pH ~ 0 and 5.75 mol L -1 H + ), with high concentrations of some plant nutrients, such as S-SO 4 2-(791 g L -1 ), N-NO 3 -(18 g L -1 ), Cl-Cl -(128 g L -1 ), P-PO 4 3-(19 g L -1 ), Fe (13,595 mg L -1 ), K (3,438 mg L -1 ), and Mn (1,199 mg L -1 ) (Santos et al, 2016).…”

Radiação síncrotron na agricultura e ciência do solo

“…Na agricultura, nutrientes das plantas, como fósforo e micronutrientes que estão fortemente ligados a sólidos do solo, são de particular interesse porque a solubilização desses elementos no solo determina sua absorção pelas plantas. A vasta gama de energia abrangida pelas várias linhas de luz do Sirius permitirá a continuidade de estudos sobre a troca de cálcio pelo tóxico alumínio em solos agrícolas que receberam calagem, a liberação de nutrientes a partir de resíduos e reuso de subprodutos da indústria em rotas alternativas de produção de fertilizantes (8), bem como a química da interface raiz-solo (rizosfera) para melhorar a absorção de nutrientes, evitando a absorção de elementos tóxicos. química em solos, que são potencialmente mais complexos que modelos convencionais baseados em processos termodinâmicos e cinéticos de análogos químicos puros desses componentes presentes no solo.…”