The first is the water washing method which can remove a large amount of soluble phosphorus and fluorine However due to secondary wastewater and high investment costs this method is difficult to apply in the industrial field The second is the traditional flotation method which can remove organic matter suspended in PG slurry
·Phosphogypsum PG is an industry solid waste produced from phosphoric acid manufacture To reduce environmental pollution of the PG H 2 C 2 O 4 was employed to purify it which then can be used for cement optimal concentration of H 2 C 2 O 4 for PG purification was determined In addition differential thermal analysis DTA X ray
It can be concluded that water washing pre treatment greatly improves the workability and mechanical property of PG based CPB These results are of great value for creating a reliable and environmentally superior alternative for the recycling of PG and for safer mining production KW Cemented paste backfill KW Phosphogypsum KW Purification
·Phosphogypsum PG is an industry solid waste produced from phosphoric acid manufacture To reduce environmental pollution of the PG H 2 C 2 O 4 was employed to purify it which then can be used for cement production The optimal concentration of H 2 C 2 O 4 for PG purification was determined In addition differential thermal analysis DTA X ray
·Water washing can remove a certain number of soluble impurities from the surfaces of PG crystals and greatly improve the workability and mechanical properties of PG based cemented paste backfill CPB After 7 14 and 28 days of curing the unconfined compressive strength values of the purified PG filled CPBs reached and
·Phosphogypsum PG is a major industrial waste emitted during phosphate production thermal treatment and synergistic treatment by various means are effective methods for cleaning PG and future treatment processes should be developed to highly efficient and low cost The calcination can effectively remove soluble salts and organic
·The raw material was treated to remove additional water and impurity by washing air drying and oven drying Both treated and untreated materials were used in experimental work
The principle of water washing method the main impurity affecting the phosphogypsum can dissolve in organic impurities mainly for oily substances above can float on the water washing method can remove most of the phosphorus gypsum soluble impurities including phosphorus fluorine most alkali metal salts and organic
2 ·phosphogypsum leachate in Section pH was adjusted at / 12 at 25˚C ± 5˚C and 400 r/min the reaction was carried out for 24 hours aged for 12 hours filtered and the precipitate was dried in an oven at 100˚C 5 mL of the filtrate was taken and dried using the method described in Section Test the concentration of phosphorus pentoxide
·Recycling phosphogypsum PG for cemented paste backfill CPB has been widely used at phosphate mines in China However the impurities in PG prolong the setting time and reduce the uniaxial compressive strength UCS limiting the engineering application of PG This paper aims to investigate the feasibility of treated PG TPG washed repeatedly using
·Among common pretreatments washing can remove harmful impurities including soluble phosphorus soluble fluorides organic matter and residual acid which can significantly improve the properties of PG [8] However it is likely to increase the economic cost and cause secondary pollution [12] Calcination pretreatment shows a good effect on removing
·The current trends focus on purifying PG by different methods 1 water washing which could remove dissolved phosphorus and fluorine but wastewater treatment as a byproduct is a major concern and the solution is not effective for eutectic phosphorus removal 4; 2 floatation method can remove the organic matter but the phosphorus and
·Phosphogypsum PG waste is a by product generated from wet process phosphoric acid H3PO4 manufacturing during phosphate rock decomposition Worldwide the annual production of PG ranges between 100 and 300 million tons with only a few quantities utilized in several application domains about 15% the unused PG is usually discharged into
·As both CaHPO 4 ·2H 2 O and CaSO 4 ·2H 2 O belong to monoclinic crystal system and possess comparable lattice constants HPO 4 2− can easily replace part of SO 4 2− during the production of wet process phosphoric acid and enter the calcium sulfate lattice thus forming eutectic phosphorus By comparing the FTIR spectra of PG raw materials CaHPO 4
·Phosphogypsum PG is an industrial by product of the transformation of phosphate rocks For decades PG has been a source of environmental concern due to the massive amount produced thus far 7 billion tons with a current production rate of 200 280 million tons per year Phosphate minerals contain various impurities that precipitate and
·Phosphogypsum washing and drying equipment 2020 This set of phosphogypsum washing and drying equipment adopts the sieving washing and grading process flow that is the phosphogypsum is first sieved to remove large particles larger than 25 mm and then added to the grinding tank to grind into a slurry with water and the slurry is removed by
·phosphogypsum can be removed by treating it with various acids and reagents [11] It is also reported that both organic and inorganic acids can extract trapped phosphorous from phosphogypsum [12]
·The most commonly used pretreatment methods of phosphogypsum are lime water washing or neutralization The water soluble P and F impurities can be converted into insoluble Ca 3 PO 4 2 and CaF 2 to improve the quality of phosphogypsum Chen et al 2019; Singh and Garg 2000 Singh 2002 pretreated phosphogypsum with a citric acid solution
·by washing PG with varying solid liquid S/L ratios and stirring times Although the water washing method has been studied for decades most of the previous studies usually washed PG for only
with TBP extraction can remove impurities wrapped in PG and the whiteness of the purified gypsum can reach more than 90% Zhao 2017 Zhao used a single extraction process of sulfuric acid combined with TBP to treat phosphogypsum containing % SiO 2 TBP and PG were then combined with 30
·As both CaHPO 4 ·2H 2 O and CaSO 4 ·2H 2 O belong to monoclinic crystal system and possess comparable lattice constants HPO 4 2− can easily replace part of SO 4 2− during the production of wet process phosphoric acid and enter the calcium sulfate lattice thus forming eutectic phosphorus By comparing the FTIR spectra of PG raw materials CaHPO 4
·Phosphogypsum PG is reused as aggregate in the cemented backfill which effectively improves the PG reutilization efficiency However the massive impurities contained in aggregate PG would adversely affect the hydration of binder and therefore deteriorate the strength development of backfill This research starts with the feasibility study on pretreating
·in phosphogypsum can be found in the particle size fractions above 160 and below 25 µm There are more than few plants those of "Onoda" in Japan "Giulini chemic GmbH" "Knauf" in Germany etc where the impurities are eliminated by washing phosphogypsum with water or separating off coarse and very fine parti cles
