Super-stable mineralization effect of layered double hydroxides for heavy metals: Application in soil remediation and perspective

Built-In Electric Field in Freestanding Hydroxide/Sulfide Heterostructures for Industrially Relevant Oxygen Evolution

Alkaline water electrolysis (AWE), as a premier technology to massively produce green hydrogen, hinges on outstanding oxygen evolution reaction (OER) electrodes with high activity and robust stability under high current densities. However, it is often challenged by issues such as catalytic layer shedding, ion dissolution, and inefficient bubble desorption. Herein, a scalable corrosion-electrodeposition method is presented to synthesize nickel-iron layered double hydroxide (NiFe-LDH)/Ni3S2 heterostructures on nickel mesh, tailored to meet the stringent requirements of industrial AWE. The study underscores the critical role of the built-in electric field (BEF) in optimizing electronic properties, curtailing Fe leaching, and enhancing mass transfer. The resultant NiFe-LDH/Ni3S2 heterostructure manifests remarkable OER performance, with ultra-low overpotentials of 202 mV at 10 mA cm-2 and 290 mV at 800 mA cm-2 in 1.0 m KOH at 25 °C, alongside superior steady-state stability and resistance to reverse current under fluctuating conditions. Furthermore, the performance is further validated in an alkaline electrolyzer, achieving a large current density of 800 mA cm-2 at a cell voltage of 1.908 V, while maintaining excellent stability. This work offers a blueprint for the design of efficient OER electrodes for industrially relevant AWE applications.

A global systematic review and meta-analysis of innovative technologies for 1,2,4-trichlorobenzene remediation in soil and water

The 1,2,4-trichlorobenzene (1,2,4-TCB) is a persistent organic pollutant, which poses a serious concern due to its long-lasting and detrimental impact on soil and water quality. This study uses meta-analysis to investigate the effectiveness of various remediation methods for 1,2,4-TCB in water and soil. In water, the intimate coupling of photocatalysis and biodegradation (ICPB) demonstrated the highest removal rate (80%), followed by photocatalysis (PC, 69%), bioremediation (B, 53%), and photolysis (P, 42%). Optimal conditions for 1,2,4-TCB removal in water included short remediation times (< 5 days), higher temperatures (≥ 25 °C), neutral pH, and specific free radicals (H+ > •OH > •O2-). In soil, short-term remediation methods and suspended cultures showed higher removal rates. Topsoil depth layers (≤ 10 cm) exhibited better removal rates than subsoil (> 10 cm). Key factors influencing remediation effectiveness in water were hydraulic retention time (HRT), salinity, and water table depth, while in soil, remediation time and soil depth layer were the most significant. This research highlights the importance of optimizing remediation methods and environmental conditions to remove 1,2,4-TCB from contaminated sites effectively. Further investigation is needed to understand the underlying mechanisms and optimal conditions for these remediation methods, particularly in soil. Effective remediation of 1,2,4-TCB requires a tailored approach considering specific environmental conditions and challenges in water and soil. The ICPB shows promise, especially in aquatic environments. However, further research is essential to optimize these methods, particularly for soil remediation.

Representative modeling of biocompatible MXene nanocomposites for next-generation biomedical technologies and healthcare

MXenes are a class of 2D transition metal carbides and nitrides (Mn+1XnT) that have attracted significant interest owing to their remarkable potential in various fields. The unique combination of their excellent electromagnetic, optical, mechanical, and physical properties have extended their applications to the biological realm as well. In particular, their ultra-thin layered structure holds specific promise for diverse biomedical applications. This comprehensive review explores the synthesis methods of MXene composites, alongside the biological and medical design strategies that have been employed for their surface engineering. This review delves into the interplay between these strategies and the resulting properties, biological activities, and unique effects at the nano-bio-interface. Furthermore, the latest advancements in MXene-based biomaterials and medicine are systematically summarized. Further discussion on MXene composites designed for various applications, including biosensors, antimicrobial agents, bioimaging, tissue engineering, and regenerative medicine, are also provided. Finally, with a focus on translating research results into real-world applications, this review addresses the current challenges and exciting future prospects of MXene composite-based biomaterials.

Biosorption of cobalt and chromium from wastewater using manganese dioxide and iron oxide nanoparticles loaded on cellulose-based biochar: Modeling and optimization with machine learning (artificial neural network)

In this study, two nanomaterials with excellent adsorption capacities were developed to remove heavy metals efficiently from wastewater. Manganese dioxide MnO2 nanoparticles and iron oxide Fe2O3 nanoparticles were successfully synthesized using cassava peel carbon and characterized by different techniques. The experimental tests for the adsorption process were done in a batch system, and the influence of various parameters such as temperature (from 5 to 60 °C), initial concentration (from 10 to 60 mg/L), pH (2 to 8), and contact time (5 to 180 min) on the biosorption of cobalt (II) and chromium (VI) were fully investigated. Furthermore, the Qmax were 546.32 mg/g and 349.59 mg/g for chromium (VI) and cobalt (II) respectively. The results fitted Langmuir with the pseudo-second-order model, revealing that chemisorption controls heavy metals removal, while the thermodynamic sorption was an endothermic and spontaneous reaction. Artificial Neural Network (ANN) model was developed to predict as well as to simulate the experimental results, for this purpose, the proposed model was based on five independent inputs or variables and one output or response which is the predicted adsorbed amount, the proposed ANN model showed an appreciable prediction accuracy with high optimization ability for chromium (VI) and cobalt (II) removal.

Super-stable mineralization of Cu, Cd, Zn and Pb by CaAl-layered double hydroxide: Performance, mechanism, and large-scale application in agriculture soil remediation

The synthesized CaAl-layered double hydroxide (CaAl-LDH) shows excellent performance in potentially toxic metals (PTMs) removal, and the removal capacity of CaAl-LDH toward Cu²⁺, Zn²⁺ and Pb²⁺ in aqueous solution is 502.4, 315.2 and 600.0 mg/g respectively. Cu²⁺ and Zn²⁺ are removed through isomorphic substitution of laminate Ca and dissolution-reprecipitation, leading to the formation of CuAl-LDH and ZnAl-LDH mineralization products. Pb²⁺ is removed by the complexation and precipitation to form Pb₃(CO₃)₂(OH)₂. The application of CaAl-LDH in laboratory-scale soil remediation shows that target PTMs are gradually mineralized into relatively stable oxidizable and residual state, and the immobilization efficiency of available Cu, Zn, Cd and Pb reaches 84.62 %, 98.66 %, 96.81 % and 70.27 % respectively. In addition, practical application in farmland results in the significant reduction of available Cu, Zn, Cd and Pb with the immobilization efficiency of 30.15 %, 67.30 % and 57.80 % and 38.71 % respectively. Owing to the super-stable mineralization effect of CaAl-LDH, the content of PTMs in the roots, stems and grains of cultivated buckwheat also decreases obviously, and the growth and yield of buckwheat are not adversely affected but improved. The above prove that the super-stable mineralization based on CaAl-LDH is a promising scheme for the remediation of PTMs contaminated agriculture soil.

Two-dimensional photonic MXene nanomedicine

Two-dimensional (2D) transition metal carbides and nitrides (MXenes) with fascinating physicochemical properties, ultrathin lamellar structure, high specific surface area, and excellent biocompatibility have been extensively explored in biomedical applications over the past decade. Photonic MXene nanomedicine and materdicine, as one of the most burgeoning emerging treatment modalities, are of great research interest owing to their photon utilization ability and high therapeutic efficiency. This review aims to summarize and discuss the very-recent advances in engineering 2D MXenes for photonic theranostic applications. We initially concentrate on the synthesis methods, surface modification, and functionalization with respect to MXenes. Furthermore, the photonic biological applications including photonic antibacteria, photonic bioimaging, photonic therapy, and photonic theranostics are highlighted in detail with the selected paradigms. Finally, the current challenges and future directions for 2D MXene biomaterials in regard to their photonic biomedicines are discussed in depth, aiming to drive the speed of their practical applications in clinic.

Multifunctional Epoxy-Based Electronic Packaging Material MDCF@LDH/EP for Electromagnetic Wave Absorption, Thermal Management, and Flame Retardancy

The sharp reduction in size and increase in power density of next-generation integrated circuits lead to electromagnetic interference and heat failure being a key roadblock for their widespread applications in polymer-based electronic packaging materials. This work demonstrates a multifunctional epoxy-based composite (MDCF@LDH/EP) with high electromagnetic wave (EMW) absorption, thermal conductivity, and flame retardancy performance. In which, the synergistic effect of porous structure and heterointerface promotes the multiple reflection and absorption, and dielectric loss of EMW. A low reflection loss of -57.77 dB, and an effective absorption bandwidth of 7.20 GHz are achieved under the fillings of only 10 wt%. Meanwhile, a 241.4% enhanced thermal conductivity of EP is due to the high continuous 3D melamine-derived carbon foams (MDCF), which provides a broad path for the transport of phonons. In addition, MDCF@LDH/EP composite exhibits high thermal stability and flame retardancy, thanks to the physical barrier effect of MDCF@LDH combined with the high temperature cooling properties of NiAl-LDH-CO₃ ^2- . Compared with pure epoxy resin, the peak heat release rate and the total heat release rate are reduced by 19.4% and 30.7%, respectively. Such an excellent comprehensive performance enables MDCF@LDH/EP to a promising electronic packaging material.

Insights into the Superstable Mineralization of Chromium(III) from Wastewater by CuO

The removal of Cr^III ions from contaminated wastewater is of great urgency from both environmental protection and resource utilization perspectives. Herein, we developed a superstable mineralization method to immobilize Cr³⁺ ions from wastewater using CuO as a stabilizer, leading to the formation of a CuCr layered double hydroxide (denoted as CuCr-LDH). CuO showed a superior Cr³⁺ removal performance with a removal efficiency of 97.97% and a maximum adsorption capacity of 207.6 mg/g in a 13000 mg/L Cr³⁺ ion solution. In situ and ex situ X-ray absorption fine structure characterizations were carried out to elucidate the superstable mineralization mechanism. Two reaction pathways were proposed including coprecipitation-dissolution and topological transformation. The mineralized product of CuCr-LDH can be reused for the efficient removal of organic dyes, and the adsorption capacities were up to 248.0 mg/g for Congo red and 240.1 mg/g for Evans blue, respectively. Moreover, CuCr-LDH exhibited a good performance for photocatalytic CO₂ reduction to syngas (H₂/CO = 2.66) with evolution rates of 54.03 μmol/g·h for CO and of 143.94 μmol/g·h for H₂ under λ > 400 nm, respectively. More encouragingly, the actual tanning leather Cr³⁺ wastewater treated by CuO showed that Cr³⁺ can reduce from 3438 to 0.06 mg/L, which was much below discharge standards (1.5 mg/L). This work provides a new approach to the mineralization of Cr³⁺ ions through the "salt-oxide" route, and the findings reported herein may guide the future design of highly efficient mineralization agents for heavy metals.

Biomedical engineering of two-dimensional MXenes

The emergence of two-dimensional (2D) transition metal carbides, carbonitrides and nitrides, referred to MXenes, with a general chemical formula of M_n+1X_nT_x have aroused considerable interest and shown remarkable potential applications in diverse fields. The unique ultrathin lamellar structure accompanied with charming electronic, optical, magnetic, mechanical and biological properties make MXenes as a kind of promising alternative biomaterials for versatile biomedical applications, as well as uncovering many new fundamental scientific discoveries. Herein, the current state-of-the-art advances of MXenes-related biomaterials are systematically summarized in this comprehensive review, especially focusing on the synthetic methodologies, design and surface engineering strategies, unique properties, biological effects, and particularly the property-activity-effect relationship of MXenes at the nano-bio interface. Furthermore, the elaborated MXenes for varied biomedical applications, such as biosensors and biodevices, antibacteria, bioimaging, therapeutics, theranostics, tissue engineering and regenerative medicine, are illustrated in detail. Finally, we discuss the current challenges and opportunities for future advancement of MXene-based biomaterials in-depth on the basis of the present situation, aiming to facilitate their early realization of practical biomedical applications.