Efficient Iodine Removal by Porous Biochar-Confined Nano-Cu2O/Cu0: Rapid and Selective Adsorption of Iodide and Iodate Ions

Enhanced iodide removal from aqueous solutions using 3D-printed PLA scaffold coated with Cu/Cu2O nanoparticles

In nuclear power plant accidents, radioactive iodine (129I, 131I) can enter the environment, accumulate in the food chain, and pose significant health risks. We developed a novel scaffold using Cu/Cu2O nanoparticles immobilized on a polylactic acid 3D-printed scaffold for efficient iodide removal. The PLA scaffold was fabricated using a fused deposition modeling 3D printer, then surface-modified for enhanced hydrophilicity and functionalized with carboxyl groups via hydrolysis and acrylic acid grafting. Cu/Cu2O nanoparticles were immobilized on the modified surface. The adsorption capacity, determined using the Langmuir model, was 4.85 mg/g, and adsorption kinetics followed a pseudo-second-order model. The iodide removal mechanism was primarily driven by redox reactions between Cu(0), Cu(I) and iodide, leading to the formation of copper iodide (CuI), as confirmed by X-ray diffraction and Raman spectroscopy. Importantly, the Cu/Cu2O scaffold exhibited excellent structural stability during adsorption, with minimal copper leaching (<0.08 mg/L). Characterization of the Cu/Cu2O scaffold using scanning electron microscopy with energy-dispersive spectroscopy and X-ray photoelectron spectroscopy analysis supported these results. The scaffold demonstrated high selectivity for iodide ions even with competing anions. The scaffold maintained its effectiveness across a wide pH range, and continuous column tests separately confirmed its suitability for practical applications in environmental remediation and wastewater treatment systems. In summary, we successfully fabricated a 3D-printed Cu/Cu2O-PLA scaffold, demonstrated its efficient iodide removal performance, and elucidated the underlying redox-driven adsorption mechanism.

Three-Dimensional Porous Artemia Cyst Shell Biochar-Supported Iron Oxide Nanoparticles for Efficient Removal of Chromium from Wastewater

Chromium-containing wastewater poses severe threats to ecosystems and human health due to the high toxicity of hexavalent chromium (Cr(VI)). Although iron oxide nanoparticles (IONPs) show promise for Cr(VI) removal, their practical application is hindered by challenges in recovery and reuse. Herein, a novel three-dimensional porous nanocomposite, Artemia cyst shell biochar-supported iron oxide nanoparticles (ACSC@ IONP), was synthesized via synchronous pyrolysis of Fe3+-impregnated Artemia cyst shells (ACSs) and in situ reduction of iron. The optimized composite C@Fe-3, prepared with 1 mol/L Fe3+ and pyrolyzed at 450 °C for 5 h, exhibited rapid removal equilibrium within 5-10 min for both Cr(VI) and total chromium (Cr(total)), attributed to synergistic reduction of Cr(VI) to Cr(III) and adsorption of Cr(VI) and Cr(III). The maximum Cr(total) adsorption capacity was 110.1 mg/g at pH 2, as determined by the Sips isothermal model for heterogeneous adsorption. Competitive experiments demonstrated robust selectivity for Cr(VI) removal even under a 64-fold excess of competing anions, with an interference order of SO42- > NO3- > Cl-. Remarkably, C@Fe-3 retained 65% Cr(VI) removal efficiency after four adsorption-desorption cycles. This study provides a scalable and eco-friendly strategy for fabricating reusable adsorbents with dual functionality for chromium remediation.

An Electrochemical Oxidation and Intercalation Strategy for Iodide Removal Using LDHs

Radioactive iodide harms the ecosystem and human health, necessitating its immobilization to mitigate aquatic iodine pollution. Layered double hydroxides (LDHs), a family of 2D clays with intercalated anions and controllable interlayer structures, are technologically and economically viable adsorbents to eliminate various anion pollutants. However, LDHs exhibit an extremely low affinity toward iodide species. Here, an electrochemical oxidation and intercalation strategy is developed to successfully remove and immobilize iodide using LDHs. The iodide can be transformed into I2/I3 - and subsequent IO3 - ions on NiFe-LDH/CC electrode at 0.6 and 1.0 V (vs Ag/AgCl), with an iodine adsorption capacity of 962 and 355 mg g-1, respectively. I2/I3 - are adsorbed on the surface of NiFe-LDH with a weak interaction, while IO3 - inserts into the interlayer of LDH with a high affinity due to the strong hydrogen bonding and coordination between IO3 - and Ni atoms. This LDH-based electrochemical removal strategy also has high adaptability to a low iodide concentration, wide pH range, and outstanding ion selectivity. This study can lay the foundation for efficient iodide elimination and immobilization from radioactive liquids.

Cu0-Functionalized, ZIF-8-Derived, Nitrogen-Doped Carbon Composites for Efficient Iodine Elimination in Solution

The development of copper-based materials with a high efficiency and low cost is desirable for use in iodine (I2) remediation. Herein, Cu0-nanoparticles-functionalized, ZIF-8 (Zeolite Imidazole Framework-8)-derived, nitrogen-doped carbon composites (Cu@Zn-NC) were synthesized by ball milling and pyrolysis processes. The as-prepared composites were characterized using SEM, BET, XRD, XPS, and FT-IR analyses. The results showed that the morphology of ZIF-8 changed from a leaf-like structure into an irregular structure after the introduction of a copper salt and carbonization. The copper in the pyrolysis samples was mainly in the form of Cu0 particles. The presence of an appropriate amount of Cu0 particles could increase the specific surface area of Cu@Zn-NC. The subsequent batch adsorption results demonstrated that the as-fabricated composites showed high I2 adsorption amounts (1204.9 mg/g) and relatively fast dynamics in an iodine-cyclohexane solution when the Cu content was 30% and the pyrolysis temperature was 600 °C, outperforming the other Cu-based materials. The isothermal adsorption followed both Langmuir and Dubinin-Radushkevich isotherm models, while the kinetics of I2 adsorption followed a pseudo-second-order kinetic model. The activation energy (Eα) of the adsorbent was determined to be 47.2 kJ/mol, according to the Arrhenius equation. According to the experimental and DFT analyses, I2-Zn interactions and I2-Cu0 chemisorption jointly promoted the elimination of iodine. In general, this study provided an operative adsorbent for the highly effective capture of iodine in solution, which might be worth applying on a large scale.

Study on the Thermogravimetric Kinetics of Dehydrated Sewage Sludge Regulated by Cationic Polyacrylamide and Sawdust

With the continuous increase in sewage-sludge production worldwide, the pyrolytic disposal of sludge has received great attention. To build knowledge on the kinetics of pyrolysis, first, sludge was regulated using appropriate amounts of cationic polyacrylamide (CPAM) and sawdust to study their enhancing effect on dehydration. Due to the effects of the charge neutralization and skeleton hydrophobicity, a certain dose of CPAM and sawdust reduced the sludge's moisture content from 80.3% to 65.7%. Next, the pyrolysis characteristics of the dehydrated sludge regulated by CPAM and sawdust were investigated at a heating rate of 10~40 °C/min by using TGA method. The addition of sawdust enhanced the release of volatile substances and reduced the apparent activation energy of the sample. The maximum weight-loss rate decreased with the heating rate, and the DTG curves moved in the direction of high temperature. A model-free method, namely the Starink method, was adopted to calculate the apparent activation energies, which ranged from 135.3 kJ/mol to 174.8 kJ/mol. Combined with the master-plots method, the most appropriate mechanism function ultimately obtained was the nucleation-and-growth model.