Phosphorus. Phosphorus. Examples of phosphorus in food additives. Cola. Backing powder

Transcription

1 Examples of phosphorus in food additives Cola Backing powder 1

2 from Greek: (φως = light, φορέω = carry) was discovered by Henning Brand, a German pharmacist and alchemist he was searching for the Philosopher s Stone, concentrating urine by evaporation white phosphorus was formed after calcining the residue under exclusion of air white phosphorus showed an unique property phosphorescence (glowing in the dark) Phosphorescence 2

3 White phosphorus was first used as a drug due to it s unique property is highly flammable and pyrophoric (self-igniting) was used for fabrication of matches fire bombs and other weapons (additive to napalm) highly toxic White White phosphorus is the least stable, most reactive, more volatile, less dense and most toxic of all allotropes of phosphorus 3

4 Red phosphorus Crystalline and amorphous modifications in a density range of g/ccm are know as red phosphorus Is formed from white phosphorus by heating to 260 C for several hours under exclusion of air is highly flammable when combined with strong oxidants safety matches Red Red phosphorus is less reactive than the white allotrope, and it is not toxic. 4

5 Black phosphorus 3 crystalline and 1 amorphous modification with a density of 2.69 g/ccm Is formed from white or red phosphorus under high pressure It is gray-black and the structure resembles to that of graphite Has semiconductor properties Black Black phosphorus is the least reactive allotrope. It is thermodynamically stable below 550 C and it is not toxic. 5

6 Phosphate ore is the 11 th most abundant element in the lithosphere occurring as phosphate commonly as an inorganic mineral phase or as an organic molecule. Phosphate rock is the only economic source for P Marine sedimentary phosphorite formed on continental shelves by oceanic upwelling of cold water enriched in nutrients (North Africa, W- USA, Mexico, Brazil, China, Vietnam) Deposits formed by disintegration of phosphorite rocks and reworking in sea and streams (Florida) Magmatic resources: magnetite-apatite (Kiruna) apatites from nepheline syenite (Khibiny, Kola) pyroxenite and carbonatite (Palabora, SA) Phosphate ore Phosphorite 6

7 Phosphate ore Minor sources include: Guano: thick accumulation of bird excreta reacting with limestone (Christmas Island, Nauru) Aluminous phosphates from weathering of phosphate rock with local significance (Senegal) Recycling product: slag (Thomas converter) Earlier is CH: ground bones, but also marls and sandy layers (Gault, Gemsmättlischichten) Another source of phosphorus 7

8 Phosphate ore World production peaked at 166 million tons of phosphate rock 1988, subsequently falling back to ca. 140 million tons : 80% from deposits of sedimentary origin 17% form igneous rocks and their weathering derivatives Remainder: residual sedimentary and guano deposits Economically produced phosphate ore contains 20 30% P2O5 Phosphate exploitation Open pit mining methods with walking draglines (Florida) Coal mining-like techniques with blasting and removal by dragline/shovel (Morocco, Tunisia) Underground methods for steeply dipping deposits include room-and-pillar (North Africa) Sub-level open stoping (Kola Penninsula) Washing, crushing, sizing i and flotation ti is common in order to increase BPL to 60 88% Magnetic separation to remove iron minerals Slurries need screening and hydrocycloning to remove clay prior to flotation (Florida) 8

9 Phosphate exploitation Phosphate rock production and resources 9

10 Phosphate minerals Apatite (Fluorapatite) From Greek apatao = I m misleading Phosphate minerals Autunite 10

11 Phosphate minerals Turquoise Phosphate minerals Nearly 400 phosphate compounds are known, but only few control phosphate concentration in natural systems 11

12 is a unique element: A key element in many physiological and biochemical processes An essential nutrient for all life forms Converts energy to a usable form for food and fiber Uptake by most living organisms from natural waters But, Low solubility of phosphate minerals P is a limiting element for animal and plant productivity (Historically: overcome by recycling of manure) Phosphates Phosphate uptake by plants 12

13 Phosphates Adenosine Triphosphate (ATP); energy gain when end phosphate is released to form ADP A phosphate group is attached when a cell needs to store energy. molecular rechargeable battery Use of phosphates Phosphate rich fertilizers used to dramatically increase global agricultural production Cereals are estimated to account for 55% of fertilizer use worldwide; wheat 20%, corn 14%, rice 13%, barley 4% 13

14 Phosphoric acid Phosphoric acid is the largest inorganic acid produced and consumed by value (and only second to sulfuric acid in terms of volume). Fertilizer Feedstock of phosphates and fertilizers Cattle feed additives Food additives Detergent additives Acid cleaners Hardener for paints and varnish Synthetic rubber Etc.. Phosphoric acid Finely ground phosphate rock is mixed with water and treated with sulfuric acid. The basic reaction is: Ca 5 (PO 4 ) 3 F + 5H 2 SO H 2 O 5CaSO 4 2H 2 O + 3H 3 PO 4 + HF Hydrogen fluoride reacts with silicates to fluorosilicic acid SiO 2 + 6HF H 2 SiF 6 + 2H 2 O Formation of 1 ton of P 2 O 5 as wet process acid consumes t of phosphate rock (70% BPL) By-products include 1.7 t phosphogypsum High content of P, F, Cl, U, Th, REE requires this gypsum to be treated as waste 14

15 Phosphates in the environment Increase of phosphate content in sewage due to use of phosphate based detergents eutrophication of rivers and lakes Ban of phosphate h base detergents t in Switzerland (since 1985) caused a reduction of 70% of phosphate input Agricultural phosphate release to natural waters usually cannot be attributed to leaching of fertilizers But rather to increased use of phosphate-rich p manure Phosphate-rich manure is mainly a consequence of feeding with off-site produced cattle feed Challenges for earth scientists Improve ability to limit mobilization of phosphorus from agricultural and other human sources to natural waters Developing designer fertilizer with formulations that allow better control of phosphorus release Methods to recycle phosphorus from waste (sewage sludge and effluents) Taking advantage in low solubility of phosphate minerals and focus research to design methods to immobilize toxic and radioactive waste 15

16 Use of sewage sluge as fertilizer is not allowed Fertilizer from in Switzerland (since 2008) incinerated Sewage is incinerated and disposed in landfills sewage sludge g P per kg ash from incinerated sewage sludge 6100 t P in Switzerland per year A research project started by the Paul-Scherrer- Institute led to development of a thermochemical treatment of the ash for separation from heavy metals R lt f tili l t ith l bl Result: fertilizer granulate with soluble phosphorus 16