Carbon-based electroactive ion exchange materials: Ultrahigh removal efficiency and ion selectivity for rapid removal of Cs+ ions

Facile One-Step Pyrolysis of ZnO/Biochar Nanocomposite for Highly Efficient Removal of Methylene Blue Dye from Aqueous Solution

In this work, we developed a facile one-step pyrolysis method for preparing porous ZnO/biochar nanocomposites (ZBCs) with a large surface area to enhance the removal efficiency of dye from aqueous solution. Peanut shells were pyrolyzed under oxygen-limited conditions with a molten salt ZnCl2, which played the roles of the activating agent and precursor for the formation of nanoparticles. The effects of the mass ratio between the molten salt ZnCl2 and peanut shells as well as pyrolysis temperature on the formation of ZBCs were investigated. Characterization results revealed that the as-synthesized ZBCs exhibited a highly porous structure with a specific surface area of 832.12 m2/g, suggesting a good adsorbent for efficient removal of methylene blue (MB). The maximum adsorption capacity of ZBCs on MB was 826.44 mg/g, which surpassed recently reported adsorbents. The formation mechanism of ZnO nanoparticles on the biochar surface was due to ZnCl2 vaporization and reaction with water molecules extracted from the lignocellulosic structures. This study provides a basis for developing a simple and large-scale synthesis method for wastewater with a high adsorption capacity.

Efficient Co-Adsorption and Highly Selective Separation of Cs+ and Sr2+ with a K+ -Activated Niobium Germanate by the pH Control

¹³⁷ Cs and ⁹⁰ Sr are hazardous to ecological environment and human health due to their strong radioactivity, long half-life, and high mobility. However, effective adsorption and separation of Cs⁺ and Sr²⁺ from acidic radioactive wastewater is challenging due to stability issues of material and the strong competition of protons. Herein, a K⁺ -activated niobium germanate (K-NGH-1) presents efficient Cs⁺ /Sr²⁺ coadsorption and highly selective Cs⁺ /Sr²⁺ separation, respectively, under different acidity conditions. In neutral solution, K-NGH-1 exhibits ultrafast adsorption kinetics and high adsorption capacity for both Cs⁺ and Sr²⁺ (q_m ^Cs  = 182.91 mg g^-1 ; q_m ^Sr  = 41.62 mg g^-1 ). In 1 M HNO₃ solution, K-NGH-1 still possesses q_m ^Cs of 91.40 mg g^-1 for Cs⁺ but almost no adsorption for Sr²⁺ . Moreover, K-NGH-1 can effectively separate Cs⁺ from 1 M HNO₃ solutions with excess competing Sr²⁺ and M^{n +} (M^{n +}  = Na⁺ , Ca²⁺ , Mg²⁺ ) ions. Thus, efficient separation of Cs⁺ and Sr²⁺ is realized under acidic conditions. Besides, K-NGH-1 shows excellent acid and radiation resistance and recyclability. All the merits above endow K-NGH-1 with the first example of niobium germanates for radionuclides remediation. This work highlights the facile pH control approach towards bifunctional ion exchangers for efficient Cs⁺ /Sr²⁺ coadsorption and selective separation.

Remediation of environmental toxicants using carbonaceous materials: opportunity and challenges

Adsorption and photocatalytic properties of carbonaceous materials, viz., carbon nanotubes (CNTs), fullerene, graphene, graphene oxide, carbon nanofiber nanospheres, and activated carbon, are the legitimate weapons for the remediation of emerging and persistent inorganic/organic contaminants, heavy metals, and radionucleotides from the environment. High surface area, low or non-toxic nature, ease of synthesis, regeneration, and chemical modification of carbonaceous material make them ideal for the removal of toxicants. The research techniques investigated during the last decade for the elimination of environmental toxicants using carbonaceous materials are reviewed to offer comprehensive insight into the mechanism, efficiency, applications, advantages, and shortcomings. Opportunities and challenges associated with carbon materials have been discussed to suggest future perspectives in the remediation of environmental toxicants.

An electroactive montmorillonite/polypyrrole ion exchange film: Ultrahigh uptake capacity and ion selectivity for rapid removal of lead ions

Contact with trace heavy metal contaminants will also lead to extremely bad health influence on human body and aquatic life. Although various adsorbents have been synthesized for the recovery of heavy metal ions, most of them shows deficient adsorption capacity, sluggish uptake rate and low selectivity. In this study, a montmorillonite/polypyrrole (MMT/PPy) film was successfully synthesized by intercalating polymers PPy into the interlayer of MMT nanosheets for selective and rapid capture of Pb²⁺. The electroactive film has ultrahigh uptake capacity (1373.29 mg⋅g^-1), which is much higher than most conventional Pb²⁺ adsorbents. Meanwhile, it had an extreme selectivity towards Pb²⁺ due to the MMT/PPy film can accurately identified Pb²⁺. Through characterization testing and data analysis, the selective and rapid uptake/release of Pb²⁺ should be realized through three ways: (1) negatively-charged laminates of MMT can generate electrostatic attraction to Pb²⁺; (2) -OH on the surface of MMT laminates can accurately identified and bonded with Pb²⁺ (M-O-H↔ M-O-Pb); (3) PPy doped by PSS^n- and protic acid can rapidly catch Pb²⁺ (PPy⁺·PSS^n-+Pb²⁺+e^-→ PPy·PSS^n-·Pb²⁺). Therefore, such a novel MMT/PPy nanocomposite film could has evident application prospect to remove Pb²⁺ from various water bodies.