The Challenges of Reusing Mining and Mineral-Processing Wastes

Bian, Zhengfu; Miao, Xiaoyu; Lei, Shaogang; Chen, Shen-En; Wang, Wenfeng; Struthers, Sue

doi:10.1126/science.1224757

Cited by 340 publications

(163 citation statements)

References 17 publications

Supporting

Mentioning

159

Contrasting

Unclassified

Order By: Relevance

“…31,32 In the precipitate samples, Cd−Cd paths were observed at the distance of 3.54 Å with 8.8 Cd atoms for Cd(OH) 2 and 3.61 Å with 1.1 Cd atoms for Cd−As(III) precipitates, which were comparable with previous studies. 33,34 In the Cd−As(III)−TiO 2 samples, no Cd−Cd paths were detected, indicating that no Cd(OH) 2 or Cd−As(III) precipitates existed (Table S9 of the Supporting Information). 32 When the As(III) concentration was low (R = 0.5), Cd bonded with 0.6 Ti and 0.5 As atoms, while in the presence of elevated concentrations of As(III) (R = 15.8), only 0.6 As atoms were resolved in the second shell around each Cd atom.…”

Section: Methodsmentioning

confidence: 99%

Molecular Insights into Ternary Surface Complexation of Arsenite and Cadmium on TiO₂

Chan

et al. 2015

Environ. Sci. Technol.

View full text Add to dashboard Cite

Insights from molecular-level mechanisms of arsenite [As(III)] and cadmium (Cd) co-adsorption on TiO 2 can further our understanding of their synergistic removal in industrial wastewaters. The motivation for our study is to explore the interfacial interactions of neutrally charged As(III) and cationic Cd 2+ on nanocrystalline TiO 2 using multiple complementary techniques. The results of adsorption edge, ζ potential, and surface complexation modeling suggest that coexistence of As(III) and Cd 2+ enhanced their synergistic adsorption on TiO 2 and, consequently, resulted in the formation of a ternary surface complex. This ternary surface complex, in turn, inhibited the metal release into the aqueous phase and, therefore, facilitated the immobilization of the heavy metals. Our in situ flow-cell attentuated total reflectance Fourier transform infrared (ATR−FTIR) spectroscopy and extended X-ray absorption fine structure (EXAFS) spectroscopy evidence showed that, regardless of the order of contact, As(III) was preferentially adsorbed on TiO 2 rather than Cd. In agreement with our spectroscopic analysis, quantum chemistry calculations also illustrated that the Cd−As(III)−TiO 2 ternary surface complex should be formed with the adsorbed As(III) as the bridging molecule. At high As(III) concentrations, the formation of the Cd−As(III)−TiO 2 complex is responsible for the Cd removal. The simultaneous removal mechanisms will further our understanding of the removal of multiple pollutants in industrial wastewaters. ■ INTRODUCTIONCoexistence of arsenic (As) and cadmium (Cd) with extremely high concentrations in mining and smelting wastewaters presents a major challenge to the environment. 1,2 Arsenate [As(V)] is the primary As species in oxic environments, whereas under reducing conditions and especially in industrial wastewaters, the more toxic and mobile arsenite [As(III)] is predominant.3−5 Simultaneous adsorptive removal of As(III) and Cd can be successfully achieved using regenerable TiO 2 . 6 However, the molecular-level interactions between cationic Cd and neutrally charged As(III) on the TiO 2 surface are poorly understood.The rapid increase in industrial mineral exploration and extraction over the past 2 decades 7 has motivated extensive studies on the interactions of metals and oxyanions on solids.8−10 The synergistic uptake of cationic metals and anionic ligands on metal oxide surfaces is generally attributed to the electrostatic effect, formation of ternary surface complexes, and surface and bulk precipitation, as evidenced by spectroscopic analysis.11−14 However, no clear boundaries exist distinguishing ternary surface complexes and surface precipitation, and these two terms sometimes are even used interchangeably.12 For example, surface precipitation was used to describe elevated As(V) removal in the presence of Zn 11 and Cu 15 on goethite. On the other hand, more recent reports use ternary surface complexation to describe the co-adsorption of cations and anions on a surface where the newly formed cation...

show abstract

Section: Methodsmentioning

confidence: 99%

Molecular Insights into Ternary Surface Complexation of Arsenite and Cadmium on TiO₂

Chan

et al. 2015

Environ. Sci. Technol.

View full text Add to dashboard Cite

show abstract

“…Smelting wastewater is usually coupled with high concentrations of As and Cd, which presents a major challenge to the environment (Bian et al, 2012;Hao et al, 2015;Liao et al, 2016;Roussel et al, 2000). TiO 2 has been investigated to simultaneously remove high concentrations of As(III) and Cd from metallurgical wastewater (Luo et al, 2010;Yan et al, 2015).…”

Section: At High Concentrations In Industrial Wastewatermentioning

confidence: 99%

Recent progress of arsenic adsorption on TiO 2 in the presence of coexisting ions: A review

Jing

2016

Journal of Environmental Sciences

View full text Add to dashboard Cite

“…As one of the major green mining technologies recently promoted and applied in China, fully-mechanized coal mining with solid backfilling [8][9][10][11][12], is not only effective in extracting "three under" coal reserves (i.e., coal trapped under buildings, water-bodies, and railways) and controlling ground subsidence, it is also instrumental in protecting the local environment and the disposing of solid waste, such as gangue, fly ash, aeolian sand, loess, and construction waste [13][14][15]. As the study of the backfilling method goes deeper and its application goes wider [16][17][18][19], the integrated technique of underground gangue washing-discharging-backfilling has been applied to cut the cost of gangue lifting and reduce the potential environmental impact caused by gangue dumping and spontaneous combustion.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Overlying Strata Movement and Behaviors in Caving and Solid Backfilling Mixed Coal Mining

et al. 2017

View full text Add to dashboard Cite

Based on techniques of close upper protective coal-rock layer mining, relieved gas extraction, and underground gangue washing-discharging-backfilling, this paper initiates the concept of mixed fully-mechanized coal mining, which combines a solid backfilling method and a caving method (hereinafter referred to as "backfill and caving mixed mining"). After the principle and key techniques are introduced, a physical simulation experiment and a numerical simulation are used to study the characteristics of the overlying strata's fracture development, the main roof subsidence, the stress field and its influence area in the transition area with the length ratios of the backfilling section and the caving section, and the advancing distance of the mixed longwall face. Thus, the lengths of the caving section and the backfilling section, the parameters of the support system in the transition section, and the design process of the mixed longwall face are presented. In practice, the mixed longwall face Ji 15 -31010 in Ping-dingshan No. 12 Colliery proves that the designed lengths of 120 m and 100 m for the backfilling section and the caving section, respectively, are appropriate. The monitoring results of the hydraulic support working resistance show that the supports were working well in general; the maximum growth height of the overlying strata fracture is 18 m; the gas drainage efficiency is up to 80% and the average gas concentration is 0.1 g/m 3 ; a large quantity of gangue generated in the Ji 14 seam is disposed underground; coal and gas are extracted simultaneously; and significant environmental and economic benefits are realized.

show abstract

The Challenges of Reusing Mining and Mineral-Processing Wastes

Cited by 340 publications

References 17 publications

Molecular Insights into Ternary Surface Complexation of Arsenite and Cadmium on TiO₂

Molecular Insights into Ternary Surface Complexation of Arsenite and Cadmium on TiO₂

Recent progress of arsenic adsorption on TiO 2 in the presence of coexisting ions: A review

Analysis of Overlying Strata Movement and Behaviors in Caving and Solid Backfilling Mixed Coal Mining

Contact Info

Product

Resources

About

The Challenges of Reusing Mining and Mineral-Processing Wastes

Cited by 340 publications

References 17 publications

Molecular Insights into Ternary Surface Complexation of Arsenite and Cadmium on TiO2

Molecular Insights into Ternary Surface Complexation of Arsenite and Cadmium on TiO2

Recent progress of arsenic adsorption on TiO 2 in the presence of coexisting ions: A review

Analysis of Overlying Strata Movement and Behaviors in Caving and Solid Backfilling Mixed Coal Mining

Contact Info

Product

Resources

About

Molecular Insights into Ternary Surface Complexation of Arsenite and Cadmium on TiO₂

Molecular Insights into Ternary Surface Complexation of Arsenite and Cadmium on TiO₂