Beneficiation, desilication and selective precipitation techniques for phosphorus refining from biomass derived fly ash
The supply of aﬀordable phosphorus (P), a biocritical element, is at great risk due to the utilization of limited natural phosphate minerals at an unprecedented scale. The need of phosphorus recovery to sustain the anthropogenic P-cycle was recog- nized and ﬂy ash, a waste product from the combustion of renewable biofuels, was selected as the secondary resource. Increasing supply of ﬂy ash in the future due to growing use of forest biofuels in energy production also contributes to its suitability for P-recovery. Fly ash comprises of silicates, oxides, carbonates, phosphates and hydroxides of the elements that potentially represent the entire periodic table. This only augments the complexity of the recovery process, since most of the interfering matrices need to be removed prior to the extraction of phosphorus. Methods for separation of impurities and extraction of the phosphorus were developed and optimized. The establishment of a relationship between the particle size and mineral content enables an elevation of the phosphorus level by a factor of 1.38, while the silicon (Si) content is reduced by a factor of 3.8 for a circulatory ﬂuidized bed derived ﬂy ash. This was achieved by the use of sieving beneﬁciation with a sieve size of 125 µm. Despite the feasibility of ﬂy ash leaching with a lower molar concentration of acid for eﬃcient dissolution of phosphorus, higher concentration of HCl at 8 M was employed. Aging of this leachate for 5 h facilitates the removal of silica with an eﬃ- ciencyof99%fromtheleachatesolutionbyprecipitationofSi-particlesand/orSi-gel formation. The Si removal rate was found to vary proportionally with temperature and the H+ and Cl– ion concentration. Chemical equilibrium calculations (in the Medusa & Hydra software) were used to identify the phosphate species in the leachate and to draft the P-recovery strate- gies. Selective precipitation of AlPO4 was identiﬁed as a feasible method to recover phosphorus from the leachate. Interference of Fe was limited by the use of chelation- based masking with ethylenediaminetetraacetic acid (EDTA) at [EDTA]/[Fe]=1 and pH of 4. An amorphous white precipitant was obtained that comprises 18.1 wt% of P, 16.3 wt% of Al and 2.18 wt% of Fe as major components and also trace elements in low concentrations. AlPO4 was further converted to struvite; a slow releasing fertilizer. The process involved dissolution of solids with 0.5 M phosphoric acid, removal of Al and metal ion impurities with 0.6 g/mL of Amberlite IR120H+ (a strongly cation exchange resin), addition of Mg2+ and NH4+sources and precipitation at pH 9.5. Prospects of leachate recirculation for leaching were also investigated to lower the use of fresh phosphoric acid. Granulated white-pure crystalline struvites containing 12.5 wt% of P were obtained. The combination of reﬁning and extraction technologies, employed in this study, contribute to elevate the P content in the ﬁnal product by a factor of the order of 10. Procuring struvite. from biomass ﬂy ash is seen as a sustainable P recycling method which promotes conservation of the natural resources used for fertilizer production. ...
PublisherUniversity of Jyväskylä
MetadataShow full item record
- Väitöskirjat 
Showing items with similar title or keywords.
The Use of Ca- and Mg-Rich Fly Ash as a Chemical Precipitant in the Simultaneous Removal of Nitrogen and Phosphorus - Recycling and Reuse Myllymäki, Pekka; Pesonen, Janne; Romar, Henrik; Hu, Tao; Tynjälä, Pekka; Lassi, Ulla (MDPI AG, 2019)The European Union’s circular economy strategy aims to increase the recycling and re-use of products and waste materials. According to the strategy, the use of industry waste material should be more effective. A chemical ...
Budhathoki, Roshan; Väisänen, Ari; Lahtinen, Manu (Elsevier BV, 2018)The prospect of phosphorus (P) recovery from siliceous fly ash was investigated. The phosphorus content in the pristine fly ash was 1.21%. Obtaining pure phosphorus products from fly ash is very challenging because of high ...
Use of Calcined Dolomite as Chemical Precipitant in the Simultaneous Removal of Ammonium and Phosphate from Synthetic Wastewater and from Agricultural Sludge Pesonen, Janne; Myllymäki, Pekka; Tuomikoski, Sari; Vervecken, Gwen; Hu, Tao; Prokkola, Hanna; Tynjälä, Pekka; Lassi, Ulla (MDPI AG, 2019)Phosphorus as phosphate and nitrogen as ammonium or nitrate are the main nutrients in wastewaters and agricultural sludges. They runoff easily to waterways and cause eutrophication in water bodies. However, ammonium and ...
Lapinkangas, Suvi; Rautio, Lasse; Kauppinen, Toni; Hu, Tao; Pesonen, Janne; Lassi, Ulla (Elsevier BV, 2022)Hazenite (KNaMg2(PO4)2 × 14 H2O), a new type of struvite mineral, was precipitated from the potassium-rich washing water of spent alkaline battery black mass. Hazenite can be used as a fertilizer, which would be an additional ...
The use of calcined paper mill sludge as a chemical precipitant in the simultaneous removal of ammonium and phosphate : paper mill waste recycling and reuse Myllymäki, Pekka; Pesonen, Janne; Romar, Henrik; Hu, Tao; Tynjälä, Pekka; Lassi, Ulla (Desalination Publications, 2020)Currently, recycling and re-use of materials is extremely important due to the diminishing of natural resources. The objective of the European Union’s circular economy strategy is to increase recycling and ...