Removal of trivalent chromium ions in model contaminated groundwater using hexagonal boron nitride as an adsorbent

The feasibility of using hexagonal boron nitride (h-BN) to treat heavy metal Cr(III) from model contaminated groundwater was evaluated in this study by adsorption experiments and characterizations. To the best of our knowledge, this study is the first attempt to conduct the adsorption of Cr(III) by h-BN under various experimental conditions such as exposure time, ratio of adsorbates and adsorbents, solution pH, background ions with different ionic strength, and the presence of humic acids (HA) in model contaminated groundwater. The optimized h-BN showed excellent maximum adsorption capacity (i.e., 177 mg ∙ g-1) when the concentrations of Cr(III) and h-BN were 10 and 10 mg ∙ L-1, respectively. Subsequently, we confirmed there was a negligible change in the adsorption performance of Cr(III) by h-BN in the presence of co-ions (i.e., K and Mg) in concentrations in a range from 50 to 1000 mg ∙ L-1. Furthermore, the adsorption performance of Cr(III) gradually improved with HA concentrations from 2.5 to 25 mg ∙ L-1. Interestingly, the maximum adsorption performance of Cr(III) by both HA and h-BN increased until 500 mg ∙ g-1 in the presence of 25 mg ∙ L-1 HA. The adsorption mechanism was clarified by Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. Additionally, we successfully confirmed that h-BN could be reused until five cycles. On the basis of the adsorption performance results and characterizations, h-BN can be utilized as an efficient and practical adsorbent to treat Cr(III) in groundwater treatment.

Adsorption of uranyl ion on hexagonal boron nitride for remediation of real U-contaminated soil and its interpretation using random forest

Acid leaching has been widely applied to treat contaminated soil, however, it contains several inorganic pollutants. The decommissioning of nuclear power plants introduces radioactive and soluble U(VI), a substance posing chemical toxicity to humans. Our investigation sought to ascertain the efficacy of hexagonal boron nitride (h-BN), an highly efficient adsorbent, in treating U(VI) in wastewater. The adsorption equilibrium of U(VI) by h-BN reached saturation within a mere 2 h. The adsorption of U(VI) by h-BN appears to be facilitated through electrostatic attraction, as evidenced by the observed impact of pH variations, acidic agents (i.e., HCl or H2SO4), and the presence of background ions on the adsorption performance. A reusability test demonstrated the successful completion of five cycles of adsorption/desorption, relying on the surface characteristics of h-BN as influenced by solution pH. Based on the experimental variables of initial U(VI) concentration, exposure time, temperature, pH, and the presence of background ions/organic matter, a feature importance analysis using random forest (RF) was carried out to evaluate the correlation between performances and conditions. To the best of our knowledge, this study is the first attempt to conduct the adsorption of U(VI) generated from real contaminated soil by h-BN, followed by interpretation of the correlation between performance and conditions using RF. Lastly, a. plausible adsorption mechanism between U(VI) and h-BN was explained based on the experimental results, characterizations, and a. comparison with previous adsorption studies on the removal of heavy metals by h-BN.

Advances in boron nitride-based nanomaterials for environmental remediation and water splitting: a review

Boron nitride has gained wide-spread attention globally owing to its outstanding characteristics, such as a large surface area, high thermal resistivity, great mechanical strength, low density, and corrosion resistance. This review compiles state-of-the-art synthesis techniques, including mechanical exfoliation, chemical exfoliation, chemical vapour deposition (CVD), and green synthesis for the fabrication of hexagonal boron nitride and its composites, their structural and chemical properties, and their applications in hydrogen production and environmental remediation. Additionally, the adsorptive and photocatalytic properties of boron nitride-based nanocomposites for the removal of heavy metals, dyes, and pharmaceuticals from contaminated waters are discussed. Lastly, the scope of future research, including the facile synthesis and large-scale applicability of boron nitride-based nanomaterials for wastewater treatment, is presented. This review is expected to deliver preliminary knowledge of the present state and properties of boron nitride-based nanomaterials, encouraging the future study and development of these materials for their applications in various fields.

Compressive and thermally stable boron nitride aerogels as multifunctional sorbents

Boron nitride (BN) aerogels are three-dimensional bulk materials with exceptional performances in a wide range of areas. However, detailed investigations into the relationship of synthesis, structure, and properties are rare. This study demonstrates the feasibility of tuning the performance of the aerogel by simply altering the relative amount of the precursors in the synthesis, which subsequently leads to the formation of aerogels with distinctive properties such as specific surface areas, porosity, and compressibility. The applications of these structurally different aerogels are exemplified by investigating in a series of important industrial-related areas, such as oil absorption/desorption, direct combustion, adsorptive desulfurisation, and CO₂ capture. The study raises the application prospects of BN aerogels in gas-phase catalysis and thermal superinsulation materials.

Boron nitride-based materials for water purification: Progress and outlook

Analogous to the carbon family, boron nitride (BN)-based materials have gained considerable attention in recent times for applications in various fields. Owing to their extraordinary characteristics, i.e., high surface area, low density, superior thermal stability, mechanical strength, and conductivity, excellent corrosion, and oxidation resistance, the BN nanomaterials have been explored in water remediation. This article critically evaluates the latest development in applications of BN-based materials in water purification with focus on adsorption, synthesis of novel membranes and photocatalytic degradation of pollutants. The adsorption of various noxious pollutants, i.e., dyes, organic compounds, antibiotics, and heavy metals from aqueous medium BN-based materials are described in detail by illustrating the adsorption mechanism and regeneration potential. The major hurdles and opportunities related to the synthesis and water purification applications of BN-based materials are underscored. Finally, a roadmap is suggested for future research to assure the effective applications of BN-based materials in water purification. This review is beneficial in understanding the current status of these unique materials in water purification and accelerating the research focusing their future water remediation applications.

Luffa sponge-derived hierarchical meso/macroporous boron nitride fibers as superior sorbents for heavy metal sequestration

Boron nitride (BN) has received tremendous attention as a promising adsorbent material. However, unsatisfactory uptake capacities over heavy metal ions limit their practical applications. Herein, we have synthesized a novel hierarchical meso/macroporous BN fibers (MBNFs) via a simple carbothermal reduction method using luffa sponge as a template. The as-obtained MBNFs comprise densely arranged parallel macrochannels on a micrometer scale, with mesopores on the surface of the channel. The resulting MBNFs exhibited remarkable adsorption performance for different heavy metal ions including Cd²⁺, Zn²⁺, Cr³⁺, and Pb²⁺ with maximum uptake capacities as high as 2989, 1885, 723, and 453 mg/g, respectively. In particular, the adsorption capacity for Cd²⁺ and Zn²⁺ exceed the highest values reported for BN materials. In addition, the MBNFs showed excellent stability to re-use for a few times. The present MBNFs materials prepared using cheap and earth abundant luffa sponge may find broad applications such as adsorbent for environmental remediation applications.

A magnetic activated sludge for Cu(ii) and Cd(ii) removal: adsorption performance and mechanism studies

In the present study, a novel magnetic activated sludge (MAS) was successfully synthesized and applied for heavy metal removal.