Bioremoval of arsenic (V) from aqueous solutions by chemically modified fungal biomass

Decoupling the adsorption mechanisms of arsenate at molecular level on modified cube-shaped sponge loaded superparamagnetic iron oxide nanoparticles

In this study, a commercial cube-shaped open-celled cellulose sponge adsorbent was modified by in-situ co-precipitation of superparamagnetic iron oxide nanoparticles (SPION) and used to remove As(V) from aqueous solutions. Fe K-edge X-ray absorption spectroscopy (XAS) and TEM identified maghemite as the main iron phase of the SPION nanoparticles with an average size 13 nm. Batch adsorption experiments at 800 mg/L showed a 63% increase of adsorption capacity when loading 2.6 wt.% mass fraction of SPION in the cube-sponge. Experimental determination of the adsorption thermodynamic parameters indicated that the As(V) adsorption on the composite material is a spontaneous and exothermic process. As K-edge XAS results confirmed that the adsorption enhancement on the composite can be attributed to the nanoparticles loaded. In addition, adsorbed As(V) did not get reduced to more toxic As(III) and formed a binuclear corner-sharing complex with SPION. The advantageous cube-shape of the sponge-loaded SPION composite together with its high affinity and good adsorption capacity for As(V), good regeneration capability and the enhanced-diffusion attributed to its open-celled structure make this adsorbent a good candidate for industrial applications.

The mycobiome in murine intestine is more perturbed by food arsenic exposure than in excreted feces

Arsenic is a global pollutant that can accumulate in rice and has been confirmed to disturb the gut microbiome. By contrast, the influence on the gut mycobiome is seldom concerned because fungi comprise a numerically small proportion of the whole gut microcommunity. To expand the detection of the mycobiome in different gut sections of mammals and investigate the influence of food arsenic on the gut mycobiome in the digestive tract, we treated mice with feeds containing different compositions of arsenic species (7.3% sodium arsenate, 72.7% sodium arsenite, 1.0% sodium monomethylarsonate, and 19.0% sodium dimethylarsinate) in rice at a total arsenic dose of 30 mg/kg. After 60 days of exposure, the feces of four different sites, the ileum, cecum, colon, and excreted feces, were collected and analyzed by internal transcribed spacer gene sequencing. Among the samples, the major fungal phyla were Ascomycota, Basidiomycota, and Zygomycota; the top 10 fungal genera were Aspergillus, Verticillium, Penicillium, Cladosporium, Alternaria, Fusarium, Ophiocordyceps, Trametes, Mucor, and Nigrospora. In control mice, along the murine digestive tract, the mycobial richness and composition were significantly changed; Aspergillus and Penicillium possessed the higher ability to be stabilized in the murine gut, and larger proportions of positive correlations were observed among the major fungi. After arsenic exposure, the fungal composition was more disturbed in the intestinal tract than in feces. Along the digestive tract, arsenic can trigger larger mycobial variations, and the sensitivities of major fungi to arsenic were changed. Thus, the murine intestinal spatial mycobiota are more perturbed than excreted fecal mycobiota after food arsenic exposure. Feces are insufficient to be selected as a representative of the gut mycobiota in arsenic exposure studies.

Review: Efficiently performing periodic elements with modern adsorption technologies for arsenic removal

Arsenic (As) toxicity is a global phenomenon, and it is continuously threatening human life. Arsenic remains in the Earth's crust in the forms of rocks and minerals, which can be released into water. In addition, anthropogenic activity also contributes to increase of As concentration in water. Arsenic-contaminated water is used as a raw water for drinking water treatment plants in many parts of the world especially Bangladesh and India. Based on extensive literature study, adsorption is the superior method of arsenic removal from water and Fe is the most researched periodic element in different adsorbent. Oxides and hydroxides of Fe-based adsorbents have been reported to have excellent adsorptive capacity to reduce As concentration to below recommended level. In addition, Fe-based adsorbents were found less expensive and not to have any toxicity after treatment. Most of the available commercial adsorbents were also found to be Fe based. Nanoparticles of Fe-, Ti-, Cu-, and Zr-based adsorbents have been found superior As removal capacity. Mixed element-based adsorbents (Fe-Mn, Fe-Ti, Fe-Cu, Fe-Zr, Fe-Cu-Y, Fe-Mg, etc.) removed As efficiently from water. Oxidation of AsO₃^3- to AsO₄^3-and adsorption of oxidized As on the mixed element-based adsorbent occurred by different adsorbents. Metal organic frameworks have also been confirmed as good performance adsorbents for As but had a limited application due to nano-crystallinity. However, using porous materials having extended surface area as carrier for nano-sized adsorbents could alleviate the separation problem of the used adsorbent after treatment and displayed outstanding removal performances.

Treatment of aqueous arsenic - A review of biosorbent preparation methods

Arsenic (As) is a worldwide human health issue with the major exposure route being the consumption of As-contaminated drinking water. Sorption is considered to be an efficient treatment method, among other technologies, for As removal from various water and wastewater matrices. There are common commercially available sorbents, however, the use of locally or regionally available biomasses have recently been of interest as potentially cost-effective and environmentally friendly alternatives. Despite these benefits, untreated biomasses often show low sorption capacity, can be too fragile, and can lead to coloration of waters when used in treatment processes. Treatment methods of biomasses can include chemical processes using acid or alkaline solutions, developing of biomass composite by deposition of activating agents, and preparation of biochars. This review includes an overview of 53 recent studies that assess a variety of biomass modification methods meant to overcome these issues such as activation with acids or bases and biomass-based composites. Furthermore, future perspectives have been provided to assist in the further optimization of methods for biomass modifications to enhance their As sorption capacities.

Bioremediation Options for Heavy Metal Pollution

BACKGROUND

Rapid industrialization and anthropogenic activities such as the unmanaged use of agro-chemicals, fossil fuel burning and dumping of sewage sludge have caused soils and waterways to be severely contaminated with heavy metals. Heavy metals are non-biodegradable and persist in the environment. Hence, remediation is required to avoid heavy metal leaching or mobilization into environmental segments and to facilitate their extraction.

OBJECTIVES

The present work briefly outlines the environmental occurrence of heavy metals and strategies for using microorganisms for bioremediation processes as reported in the scientific literature.

METHODS

Databases were searched from different libraries, including Google Scholar, Medline and Scopus. Observations across studies were then compared with the standards for discharge of environmental pollutants.

DISCUSSION

Bioremediation employs microorganisms for removing heavy metals. Microorganisms have adopted different mechanisms for bioremediation. These mechanisms are unique in their specific requirements, advantages, and disadvantages, the success of which depends chiefly upon the kind of organisms and the contaminants involved in the process.

CONCLUSIONS

Heavy metal pollution creates environmental stress for human beings, plants, animals and other organisms. A complete understanding of the process and various alternatives for remediation at different steps is needed to ensure effective and economic processes.

COMPETING INTERESTS

The authors declare no competing financial interests.

A critical review on arsenic removal from water using iron-based adsorbents

Intensive research efforts have been pursued to remove arsenic (As) contamination from water with an intention to provide potable water to millions of people living in different countries. Recent studies have revealed that iron-based adsorbents, which are non-toxic, low cost, and easily accessible in large quantities, offer promising results for arsenic removal from water. This review is focused on the removal of arsenic from water using iron-based materials such as iron-based nanoparticles, iron-based layered double hydroxides (LDHs), zero-valent iron (ZVI), iron-doped activated carbon, iron-doped polymer/biomass materials, iron-doped inorganic minerals, and iron-containing combined metal oxides. This review also discusses readily available low-cost adsorbents such as natural cellulose materials, bio-wastes, and soils enriched with iron. Details on mathematical models dealing with adsorption, including thermodynamics, kinetics, and mass transfer process, are also discussed. For elucidating the adsorption mechanisms of specific adsorption of arsenic on the iron-based adsorbent, X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) are frequently used. Overall, iron-based adsorbents offer significant potential towards developing adsorbents for arsenic removal from water.