Removal and recovery of heavy metals from soil with sodium alginate coated FeSSi nanocomposites in a leaching process
Graphical abstract
Introduction
Due to the intensive mining activities in the past years in China, the surrounding soil was severely contaminated by heavy metals (HMs) (Qing-Ren et al., 2003). Excessive HMs in soil circulation not only threatens ecological safety and human health but also is a waste of HMs resource (Fang et al., 2016). So far, effective HMs recovery from soil is still a challenge because the soil is illiquid and HMs are tightly bound with mineral substances.
Leaching technology has been widely applied to remove HMs by transferring HMs from highly contaminated soil to liquid. However, the difficulty in aftertreatment of wastewater limits its application in large scale and the excessive metal irons in leaching agent can inhibit the removal efficiency (Burckhard et al., 1995; DijkstraJohannes et al., 2004). Hence, we consider that the synergetic recovery of HMs using a combination of a novel adsorption material with the traditional leaching method. This approach could enhance the removal efficiency of HMs from soil and minimize the effort of post-processing of wastewater. In this process, the adsorption material helps to remove HMs from the leaching agent, which delays the saturation of the leaching agent. The leaching agent is only responsible for transferring HMs from soil to the adsorbents, but no longer responsible for the holding of HMs. In recent years, nanoscale zero-valent iron (nZVI), an environment-friendly nanoscale material, has raised the attention in the HMs removal due to its large specific surface area, massive surface adsorption sites, and high reductive activity (Zhu et al., 2017a; Dong et al., 2017; Liu et al., 2015). However, pure nZVI tends to easy aggregation and rapid oxidization, which could significantly decrease the removal efficiency for HMs in wastewater (Kim et al., 2013). In addition, the weak chemical interaction between HMs and nZVI is easy to be affected by some anions such as Cl−, NO3− and SO42−, which also could influence the removal efficiency of HMs (Su et al., 2014; Crane et al., 2015). Recent reports indicated that the incorporation of sulfur into nZVI, by synthesizing sulfur-modified nZVI (S-nZVI), could improve the chemical stability of HMs-S-nZVI complex, thus enhancing the removal capacity (Rajajayavel and Ghoshal, 2015; Eun-Ju et al., 2014). Meanwhile, the SiO2 seeding could increase the final Fe° proportion through increasing the reduction of crystalline and amorphous iron oxide, which, in turn, also improves the HMs removal (Su et al., 2016). Hence, in comparison with S-nZVI, the novel FeSSi could be potentially more effective for the application of HMs removal.
To improve the separation of HMs adsorbed on FeSSi nanoparticles from soil, we synthesized the gel beads using sodium alginate (SA) to coat FeSSi nanoparticles. Meanwhile, SA has been reported to decrease the aggregation of nanoparticles and improve the removal efficiency for HMs (Wu et al., 2018a; Huang et al., 2016). In this study, we first compared the characteristics and HMs removal capacity of nZVI, S-nZVI, FeSSi and SA-FeSSi. Then, the HMs recovery efficiency by SA-FeSSi in the leaching process was comprehensively investigated under different leaching conditions. The purpose of this paper is to reveal the effects and mechanisms of sulfur modification, SiO2 coupling and SA beading for the enhancement of HM removal and, to establish the optimal structures of the adsorption materials and their best operation conditions.
Section snippets
Chemicals and soil sample
The main chemicals, including sodium borohydride (NaBH4), sodium dithionite (Na2S2O4), ferrous sulfate (FeSO4·7H2O), colloidal silica, and ferric chloride (FeCl3) were purchased from Kelong Chemical Reagent and Sigma-Aldrich companies. The aged soil was highly contaminated with HMs due to previous studies (Wu et al., 2018b; Peng et al., 2019; Hou et al., 2019). The Cd, Pb, Ni and Cr in soil were the main contaminants and their concentrations were 25.80 mg/kg, 620.52 mg/kg, 734.36 mg/kg, and
Characteristics of composites
SEM and TEM images clearly showed the aggregation of nZVI, S-nZVI and FeSSi particles (Fig. 1). However, FeSSi was more dispersive with respect to nZVI and S-nZVI, which illustrated that the using of SiO2 seeding could reduce the aggregation of S-nZVI. Although, due to the van der Waals interactions, some FeSSi still formed large agglomerate (Wu et al., 2017). SA application offered much more dispersed FeSSi particles. BET analysis showed that the specific surface area of FeSSi (101.61 m2/g)
Conclusions
In this study, the gel beads of SA coated FeSSi nanoparticles (SA-FeSSi) were synthesized. The SA coating reduced the aggregation of FeSSi and increased the density of the HMs reaction sites, which significantly enhanced the HMs removal capacity of FeSSi. The leaching study indicated that SA-FeSSi could simultaneously recycle multiple HMs (Pb, Cr, Ni and Cd) from soil and HMs recovery rates were significantly influenced by leaching pH, leaching temperature, loading of adsorbent, concentrations
CRediT authorship contribution statement
Bin Wu: Conceptualization, Investigation, Data curation, Writing - original draft, Writing - review & editing, Visualization, Supervision. Ziru Wang: Investigation, Data curation, Software. Dinghua Peng: Investigation, Visualization. Ying Wang: Writing - review & editing. Tingting He: Writing - review & editing. Hao Tang: Data curation. Heng Xu: Resources, Supervision, Project administration, Funding acquisition.
Declaration of Competing Interest
None.
Acknowledgements
This study was financially supported by the National Key Research and Development Program (2018YFC1802605), the Science and Technology Project of Sichuan Province (2019JDRC0092) and the Key Research and Development Program of Sichuan Province (2017SZ0188). The authors also wish to thank Professor Guanglei Cheng and Hui Wang from Sichuan University for the technical assistance.
References (61)
- et al.
Reproducibility of the BCR sequential extraction procedure in a long-term study of the association of heavy metals with soil components in an upland catchment in Scotland
Sci. Total Environ.
(2005) - et al.
Effect of NaBH4 on properties of nanoscale zero-valent iron and its catalytic activity for reduction of p-nitrophenol
Appl. Catal. B
(2016) - et al.
Dissolution kinetics of malachite in sulphuric acid
Hydrometallurgy
(2004) - et al.
Kinetics and thermodynamics of cadmium ion removal by adsorption onto nano zerovalent iron particles
J. Hazard. Mater.
(2011) - et al.
The effects of organic acids on the leaching of heavy metals from mine tailings
J. Hazard. Mater.
(1995) - et al.
Removal of Arsenic from water using synthetic Fe7S8 nanoparticles
Chem. Eng. J.
(2016) - et al.
The role of citric acid on the phytoremediation of heavy metal contaminated soil
Chemosphere
(2003) - et al.
Distribution and phytoavailability of heavy metal chemical fractions in artificial soil on rock cut slopes alongside railways
J. Hazard. Mater.
(2014) - et al.
The influence of calcium, sodium and bicarbonate on the uptake of uranium onto nanoscale zero-valent iron particles
Chem. Eng. J.
(2015) - et al.
Impact of pig slurry and green waste compost application on heavy metal exchangeable fractions in tropical soils
Geoderma
(2010)
Stabilization of nanoscale zero-valent iron (nZVI) with modified biochar for Cr(VI) removal from aqueous solution
J. Hazard. Mater.
Heavy metals in cement and cement kiln dust from kilns co-fired with hazardous waste-derived fuel: application of EPA leaching and acid-digestion procedures
J. Hazard. Mater.
Environmental assessment of heavy metal transport and transformation in the Hangzhou Bay, China
J. Hazard. Mater.
Leaching characteristics of residual lateritic soils stabilised with fly ash and lime for geotechnical applications
Waste Manag.
Arsenic adsorption using copper (II) oxide nanoparticles
Chem. Eng. Res. Des.
Remediation performance and mechanism of hexavalent chromium in alkaline soil using multi-layer loaded nano-zero-valent iron
Environ. Pollut.
Immobilization of Cd in river sediments by sodium alginate modified nanoscale zero-valent iron: impact on enzyme activities and microbial community diversity
Water Res.
Removal of Pb(II) from aqueous solution by a zeolite–nanoscale zero-valent iron composite
Chem. Eng. J.
Effects of pH on the leaching mechanisms of elements from fly ash mixed soils
Fuel
Manipulating the morphology of nanoscale zero-valent iron on pumice for removal of heavy metals from wastewater
Chem. Eng. J.
Removal of arsenic from aqueous solution: a study of the effects of pH and interfering ions using iron oxide nanomaterials
Microchem. J.
Design and characterization of sulfide-modified nanoscale zerovalent iron for cadmium(II) removal from aqueous solutions
Appl. Surf. Sci.
Mechanism and influence factors of chromium(VI) removal by sulfidemodified nanoscale zerovalent iron
Chemosphere
Highly efficient removal of Cr(VI) from water with nanoparticulated zerovalent iron: understanding the Fe(III)-Cr(III) passive outer layer structure[J]
Chem. Eng. J.
Effect of multiple iron-based nanoparticles on availability of lead and iron, and micro-ecology in lead contaminated soil
Chemosphere
Enhanced reductive dechlorination of trichloroethylene by sulfidated nanoscale zerovalent iron
Water Res.
Removal of chromium (VI) from water using nanoscale zerovalent iron particles supported on herb-residue biochar
J. Environ. Manage.
Effects of nitrate on the treatment of lead contaminated groundwater by nanoscale zerovalent iron
J. Hazard. Mater.
Leaching of heavy metals from contaminated soils using EDTA
Environ. Pollut.
Immobilization of mercury (II) from aqueous solution using Al2O3-supported nanoscale FeS
Chem. Eng. J.
Cited by (19)
Core-shell design of UiO66-Fe<inf>3</inf>O<inf>4</inf> configured with EDTA-assisted washing for rapid adsorption and simple recovery of heavy metal pollutants from soil
2024, Journal of Environmental Sciences (China)New insights into the environmental application of hybrid nanoparticles in metal contaminated agroecosystem: A review
2024, Journal of Environmental ManagementInsight into mechanisms of heavy metal-induced natural clay aggregation
2023, Applied Clay ScienceCitation Excerpt :There are large amounts of natural nano-sized clay particles in soil and water systems. Interactions between heavy-metal cations and natural clay minerals strongly determine the activity and transfer risks of these cations in soil–water–organism systems by influencing natural clay aggregation and dispersion process (Yin et al., 2012; Shiu and Lee, 2017; Liu et al., 2018; Wu et al., 2020; Zhou et al., 2020). Mobile nano-sized clay minerals in soil and water systems can greatly increase the transport risk of heavy metals strongly bonded at the natural clay surface (McCarthy and Zachara, 1989; Ryan and Elimelech, 1996; Kretzschmar et al., 1999).
Crop growth on metal-contaminated soils using nanotechnology: remediation and management perspectives
2023, Hybrid Nanomaterials for Sustainable Applications: Case Studies and ApplicationsRemoval of heavy metals from soil with biochar composite: A critical review of the mechanism
2021, Journal of Environmental Chemical EngineeringSimultaneous removal of nitrate and diethyl phthalate using a novel sponge–based biocarrier combined modified walnut shell biochar with Fe<inf>3</inf>O<inf>4</inf> in the immobilized bioreactor
2021, Journal of Hazardous MaterialsCitation Excerpt :It can be seen in Fig. 5c that the biocarrier can be obviously attracted to the same direction by the magnet because the Fe3O4 was loaded well on the Q3 biocarrier (Zhou et al., 2020a, 2020b). It is shown in Fig. 5d that there were abundant holes in the biocarrier of the Q2 reactor, which also reasonably explains the slight removal of DEP in period 4 and the partial removal of nitrate in Periods 1–3 (Wu et al., 2020). According to the red circle in Fig. 5f and g, there were tiny aggregates combined organisms and iron oxide on the biological carriers in the Q2 and Q3 bioreactors while the Q3 bioreactor had more aggregates, and they were similar to the Fe2+ precipitation produced in the research of (Deng et al., 2020).