Using Iron Tailings for Phosphate Removal in Cemented Phosphogypsum (PG) Backfill

Abstract

Compared with the post-treatment of pollutants, such as the removal of phosphate from wastewater, it is more important to develop effective emission control strategies to reduce phosphate pollution. Phosphogypsum (PG) is a typical solid waste byproduct of phosphate production and contains high amounts of residual phosphate. In order to control the phosphate emissions during the recycling of PG aggregates for cemented backfill, another solid waste product—iron tailings (ITs)—was added during the preparation of backfill slurry. The results showed that the ITs effectively accelerated the phosphate removal in cemented PG backfill, enabling the quick reduction in the phosphate concentration to the discharge standard (<0.5 mg/L) within 15 min. This means that the emissions of phosphate to bleeding water were effectively controlled. The adsorption experiment showed that phosphate was adsorbed by the ITs, and the adsorption data fitted well with the Langmuir adsorption model (R2 = 0.98) and pseudo-second-order kinetic model (R2 = 0.99), indicating that the phosphate adsorption of ITs was a monolayer chemical adsorption. Furthermore, an unconfined compressive strength (UCS) test was performed on the backfill with the addition of ITs. Compared to the control group (without ITs), the UCS of backfill with 20% ITs increased from 1.08 MPa to 1.33 MPa, indicating that the addition of solid waste could be beneficial to the strength development of the backfill by mitigating the interference of phosphate with the hydration process. The backfill cured for 28 d was selected for the toxic leaching test, and the phosphate concentration in the leachates was always below 0.02 mg/L, indicating that ITs can effectively immobilize phosphate in backfill for a long time.

Study on the occurrence state of main components of phosphogypsum dihydrate and its impurity distribution

“…Aer the formation of CaF 2 from F dissolved in PG, the hydration process of PG-based materials is delayed, resulting in the deterioration of its initial physical and mechanical properties, the continuous leaching of phosphorus and uorine impurities from PG when used as a cementitious material for mine backll may lead to new environmental pollution issues. 15,16 To some extent, this also limits the large-scale use of phosphogypsum-based cementitious materials,and severe limitations caused by phosphorus and uorine impurities in PG against the comprehensive utilization of PG resources. 17,18 The middle and lower reaches of the Yangtze River represent signicant bases for the exploitation of phosphate rock resources and phosphorus chemical industries in China.…”

Efficient Adsorption Removal of Phosphate from Rural Domestic Sewage by Waste Eggshell-Modified Peanut Shell Biochar Adsorbent Materials

“…Different biological, chemical, and physical techniques have been created and widely applied in previous studies to manage and treat the phosphorus (P) present in wastewater [5,6]. Among these methods, the adsorption method is the most attractive since it is economically feasible and simple in real application.…”