Purification of Phosphogypsum for Use as Cement Retarder by Sulphuric Acid Treatment

Abstract

Phosphogypsum is a by-product of the wet phosphoric acid production. In this study, chemical compositions of phosphogypsum waste (PG) in Hai Phong diammonium phosphate plant (DAP1) and Lao Cai diammonium phosphate plant (DAP2) in Vietnam were surveyed for the purpose of gypsum recovery by P2O5, F removal to meet TCVN11833 for use treated gypsum as cement retarder. Studies of impurities P2O5, F, TOC removal by sulfuric acid 10 % at 28 0C was presented. The results found that the combination of a low concentration of sulfuric acid treatment, washing, lime neutralizing, and thermal treatment was successful in Phoshogypsum treatment for use as cement retarder. The cement test proved that treated PG could partially replace natural gypsum as a retarder.Keywords: phosphogypsum treatment, phosphorus pentoxide removal, calcium sulfate transition phase, cement retarder.

Preparation of CaCO3 nano and microparticles from phosphogypsum of Dinh Vu DAP plant, Viet Nam

“…Treated PG was tested, mainly composed of CaSO4.2H2O 87.5 %, non-hazardous heavy metal. [8] 300 gram of treated PG was analysed by gama spectrometry at the Insitute for Technology of Radioactive and Rare Elements. The results showed that radium, thorium activity concentrations respectively were 102.6 Bq/kg, 11.3 Bq/kg without received value of potassium activity concentration then activity concentration index:…”

“…[2] However, phosphogypsum has potential risks for the environment due to the presence of many toxic substances such as HF, H2SO4, H3PO4 acids (pH < 2.9), heavy metals, and radioactive metal salts if PG is not pretreated. [8] This paper present research at lab scale to create CaCO3 particle from PG of DAP Dinh Vu by aeration method at different reaction conditions.…”

Comparative study of fresh phosphogypsum treatment by sulfuric acid and neutralization with NaOH and CO2

“…In this study, the concentration of acid used was lower than that used in our previous study. 10 In addition, Ca(H 2 PO 4 ) 2 ⋅H 2 O and CaHPO 4 were detected on XRD (Figure 3a,b).…”

“…Our previous study on impurities removal by sulfuric acid treatment, water washing, and neutralization was studied on the laboratory scale. 10 We also implemented the previous research to receive CaCO 3 nano-microparticles that is related to three-stage process of treated PG. 11 In this research, the comparative studies between carbonatation of treated PG by NaOH and CO 2 aeration and without carbonatation conditions were implemented to elucidate the formation of CaCO 3 in situ nanomicroparticles that were received from the carbonated PG.…”

“…The impurity of Vietnamese apatite ore is high and PG does not meet the technical standard for using it directly as cement additives. Our previous study on impurities removal by sulfuric acid treatment, water washing, and neutralization was studied on the laboratory scale 10 . We also implemented the previous research to receive CaCO 3 nano‐microparticles that is related to three‐stage process of treated PG 11 .…”