Immobilization of phosphogypsum for cemented paste backfill and its environmental effect

The main objective of this study is to control the hydration reaction rate of cement during its production process as phosphogypsum could be used as a substitute to natural gypsum in cement industry. However, the phosphogypsum impurities are pushing towards developing an efficient way to clean it due to their negative effect in hindering its use as an additive to the cement industry. The aim of this article is to treat phosphogypsum to be used in cement industry. To fulfil the purpose, samples from the Jordanian phosphogypsum were treated by washing with calcium hydroxide solution and then analyzed using X-ray Fluorescence Spectrometer. The analyses result of the treated samples indicated that the P2O5 percentage was reduced by around 16% after three times washing, whereas 100% removal of U was achieved. The reduction of SiO2 and Al2O3 were 42% and 20%, respectively. Ti content was reduced by 20%. According to the analyses, the radiation from phosphogypsum was negligible. Therefore, the treated Jordanian phosphogypsum can be used in cement industry. This will contribute to the reduction of waste phosphogypsum which considered as environmental concern from one side and provide cement industry with low cost raw material on the other side.

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“…Another study for using 0-30% cement replacement by phosphogypsum also gave maximum flexural strength with 10% phosphogypsum [22].…”

Section: Introductionmentioning

confidence: 93%

Calcium Hydroxide Washing Treatment of Jordanian Phosphogypsum for Utilization as Raw Material in Cement Industry

Al-Shawabkeh¹,

Abu-Hamatteh²,

Saadeh³

et al. 2019

EESRJ

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“…However, the cumulative quantity of PO 4 3− was much less compared to those of F − and SO 4 2− in the leachates, as shown in Figure 5. The hydration reactions would provide an alkaline environment and a great amount of calcium ions for the precipitation of F − , SO 4 2− and PO 4 3− [12]. However, the solubility product constant of calcium phosphate (2.0 × 10 −29 ) was several orders of magnitude lower than those of calcium fluoride (5.3 × 10 −9 ) and calcium sulfate (9.1 × 10 −6 ), resulting in a lower leaching quantity of PO 4 3− in the leachate under long-term immersion (as shown in Figure 5d).…”

Section: Effects Of Slurry Preparation On Leaching Behavior Of Impurimentioning

confidence: 99%

“…Therefore, it is extremely urgent to find an effective way to consume such a large amount of phosphogypsum. Alternatively, it has been estimated that about 60% of PG generated could be consumed by using PG as the aggregates in the backfill process [12]. In the cemented PG backfill process, the PG together with the hydraulic binder, water and some additives were mixed homogeneously to form a slurry on the land surface, and then the prepared slurry was transported to the underground stopes by gravity or pumping.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, impurities in the bleeding water and the leachates would transfer into the groundwater, causing environmental pollution. Li et al [12] showed that impurities in PG could be well solidified by comparing the concentrations of phosphate, sulfate and fluoride before and after the cementation. However, the question of whether the slurry preparation could affect the environmental behavior of cemented PG backfill has not been studied yet.…”

Section: Introductionmentioning

confidence: 99%

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Slurry Preparation Effects on the Cemented Phosphogypsum Backfill through an Orthogonal Experiment

Zhou

Zhu

et al. 2019

Minerals

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The cemented phosphogypsum (PG) backfill technique provides a new method for massive consumption of PG, and therefore alleviating the environmental pollution of PG. This study considered the effects of slurry preparation on the performance of cemented PG backfill. A L 16 (4 4 ) orthogonal experiment was designed to analyze four factors, namely the solid content, phosphogypsum-to-binder ratio (PG/B ratio), stirring time and stirring speed, with each factor having four levels. According to the range analysis, the solid content played the dominant role in controlling the bleeding rate, while the setting times strongly depended on the PG/B ratio. In terms of strength development of the backfill, the PG/B ratio was shown to be the most significant factor determining the unconfined compressive strength (UCS), followed by the solid content, stirring time and stirring speed. Furthermore, the results showed that the slurry preparation affected the environmental behavior of impurities that originated in PG. By analyzing the concentrations of impurities in the bleeding water of the slurry as well as the leachates of the tank leaching test, the results showed that the release of F − and SO 4 2− was aggravated clearly with the increase in the PG/B ratio, while the release of PO 4 3− always remained at relatively low levels.

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“…ere are several approaches for dealing with the surface subsidence areas, including (1) backfilling the solid wastes such as waste rocks into the subsidence area; (2) turning the tailings into filter cakes to backfill the subsidence area; (3) transforming the subsidence area into tailing ponds; and (4) blasting the rock mass around the subsidence area for backfill material [33][34][35][36]. Among these solving approaches, the approaches 1, 2, and 3 can deal with not only the surface subsidence area but also the waste rocks and tailings, thus obtaining both economic and environmental benefits.…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulation of Surface Subsidence and Backfill Material Movement Induced by Underground Mining

Wang

et al. 2019

Advances in Civil Engineering

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Surface subsidence induced by underground mining is one of the challenging problems in mining engineering, which can destroy ground surface buildings and cause huge economic losses to the mine. In this study, a two-dimensional numerical model, established by the discrete element method code PFC2D, was adopted to investigate the mechanical mechanism of surface subsidence and backfill material movement induced by underground mining in the Hongling lead-zinc mine. In the first simulation case, the ore body was excavated from the ground surface to the mining level 705 m by the sublevel caving mining method, and the stress evolution during the mining process was analyzed to reveal the mechanical mechanism of surface subsidence. In the second and third simulation cases, the mined-out areas above 905 m were backfilled by the noncemented tailings and an insulating pillar was reserved beneath the backfill material, and then the deep ore body was excavated by two different mining methods to study the movement law of the backfill material and rock strata induced by underground mining. The numerical simulation results show that when the sublevel caving mining method is adopted, underground mining can induce toppling failures in the hanging wall and lead to a large collapse pit in the ground surface. After the toppling failures in the hanging wall, the collapsed waste rock in the mined-out area can provide support force for the surrounding rock and restrict the further collapse of the hanging wall. Furthermore, when the cut-and-fill mining method is adopted for the excavation of deep ore body, the insulating pillar can restrict the horizontal displacement of surrounding rock and maintain the stability of the backfill material. The cut-and-fill mining method can efficiently control the surface subsidence and prevent the occurrence of collapse pit in the ground surface and is recommended for the Hongling lead-zinc mine to solve the surface subsidence problem.

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Immobilization of phosphogypsum for cemented paste backfill and its environmental effect

Cited by 177 publications

References 30 publications

Calcium Hydroxide Washing Treatment of Jordanian Phosphogypsum for Utilization as Raw Material in Cement Industry

Calcium Hydroxide Washing Treatment of Jordanian Phosphogypsum for Utilization as Raw Material in Cement Industry

Slurry Preparation Effects on the Cemented Phosphogypsum Backfill through an Orthogonal Experiment

Numerical Simulation of Surface Subsidence and Backfill Material Movement Induced by Underground Mining

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