Nanoporous carbons based on coordinate organic polymers as an efficient and eco-friendly nano-sorbent for adsorption of phenol from wastewater

Crab shell-based hierarchical micro/meso-porous carbon as an efficient nano-adsorbent for CO2/CH4 separation: experiments and DFT modeling

In this study, we prepared a range of nanoporous carbon nano-adsorbents from crab shells (CSs) using KOH activation and evaluated their suitability for selective adsorption of CO2/CH4 gas mixtures. We employed various characterization techniques, including XRD, FT-IR, SEM, Raman, TGA, and BET analysis, to assess the properties of these nano-adsorbents. Our investigation includes the systematic study of various parameters, such as activation time, activation temperature, and the KOH to CS activating agent ratio. The nanoporous carbons were evaluated for their CO2 adsorption capabilities at 1-10 bar and 25 ℃ condition. The results demonstrated that the CS-2-2-900 sample, activated for 1 h at 900 ℃ with a 2:1 ratio of KOH to CS, exhibited the highest gas adsorption capacity, reaching 7.217 mmol/g at a pressure of 10 bar under room temperature conditions. Additionally, the synthesized CS-2-2-900 sample displayed excellent surface area (914.85 m2/g), a pore volume of 1.1 cm3/g, and an average pore diameter of 4.82 nm. Furthermore, we functionalized the CSs to enhance their selectivity for ammonia adsorption. Using the Myers and Pravnitz theory, we calculated that the FCS-2-2-900 sample exhibited the highest selectivity, reaching 18.99 at 25 ℃ under pressures of up to 10 bar. To gain a more comprehensive understanding of the interactions between the adsorbents and the adsorbed molecules, as well as to identify the active sites involved in the adsorption process, we employed density functional theory (DFT). Our DFT calculations revealed that pyrrolic nitrogen and carboxylic sites played a significant role in enhancing the separation of CO2 in binary mixtures. In summary, nanoporous carbons derived from crab shells outperformed those derived from other waste materials. These functionalized porous nanocarbons represent promising adsorbents for the selective adsorption of CO2 gas in CO2/CH4 mixtures due to their nitrogen content, high porosity, stability, and economic efficiency.

Lignin nanoparticles as a highly efficient adsorbent for the removal of methylene blue from aqueous media

This work demonstrated enhanced adsorption capabilities of lignin nanoparticles (LNPs) synthesized via a straightforward hydrotropic method compared to pristine lignin (PL) powder for removing methylene blue dye from aqueous solutions. Kraft lignin was used as a precursor and p-toluenesulfonic acid as the hydrotrope to produce spherical LNPs with ~ 200 nm diameter. Extensive characterization by SEM, AFM, DLS, zeta potential, and BET verified successful fabrication of microporous LNPs with fourfold higher specific surface area (14.9 m2/g) compared to PL (3.4 m2/g). Significantly reduced particle agglomeration and rearranged surface chemistry (zeta potential of -13.3 mV) arising from the self-assembly of lignin fractions under hydrotropic conditions enabled the application of LNPs and superior adsorbents compared to PL. Batch adsorption experiments exhibited up to 14 times higher methylene blue removal capacity, from 20.74 for PL to 127.91 mg/g for LNPs, and ultrafast equilibrium uptake within 3 min for LNPs compared to 10 min for PL. Kinetic modeling based on pseudo-first-order and pseudo-second-order equations revealed chemisorption as the predominant mechanism, with a rate constant of 0.032825 g/mg·h for LNPs-over an order of magnitude higher than PL (0.07125 g/mg·h). Isotherm modeling indicated Langmuir monolayer adsorption behavior on relatively uniform lignin surface functional groups. The substantially augmented adsorption performance of LNPs arose from the increased surface area and abundance of surface functional groups, providing greater accessibility of chemically active binding sites for rapid dye uptake. Overall, this work demonstrates that tailoring lignin nanoparticle structure and surface chemistry via scalable hydrotropic synthesis is a simple and sustainable approach for producing highly efficient lignin-based nano-adsorbents for organic dye removal from industrial wastewater.

Effective adsorption of amoxicillin by using UIO-66@ Cr-MIL-101 nanohybrid: isotherm, kinetic, thermodynamic, and optimization by central composite design

In this research, the amoxicillin (AMX) removal was studied on a prepared nanosorbent from MOFs. The aim of this research work is to prepare nanohybrids based on metal-organic frameworks (MOFs) as an efficient nanosorbent for the absorption of amoxicillin drug. In this study, UIO-66 nanoparticles (UIO-66 NPs) were prepared from Zirconium (Zr) metal and 1,4-benzene dicarboxylic acid (BDC). Then UIO-66@Cr-MIL-101 nanohybrid was synthesized by hydrothermal method. Structural and physicochemical properties of nanohybrid UIO-66@Cr-MIL-101 were characterized by different analyses such as X-ray diffraction analysis (XRD), fourier transform infrared spectrometer (FT-IR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), transmission electron microscopy (TEM), therapeutic goods administration (TGA), and Brunauer-Emmett-Teller (BET). The effect of four fundamental variables effective on adsorption was optimized by the central composite response surface methodology (CCRSM). This parameters including loading percentage of Cr-MIL-101 NPs (10-30%), initial concentration of AMX (20-140 mg L-1), contact time (20-60 min), and pH (20-10). The removal percentage (Re%) of AMX equal to 99.50% was obtained under the following conditions: The loading value of 20% Wt%, the initial concentration of AMX 80 mg L-1, contact time 20 min, and pH = 6. Also, the experimental data were investigated with famous kinetic models and isotherms, and it was observed that AMX removal by nanohybrid is correlated with the PSO kinetic model and Langmuir isotherm.