Honeycomb-like cork activated carbon with ultra-high adsorption capacity for anionic, cationic and mixed dye: Preparation, performance and mechanism.

Herein, the cork activated carbon (CAC) with excellent adsorption performance for cationic dye, anionic dye, and mixed dye was obtained by a two-step pyrolysis method. The CAC exhibits a fluffy honeycomb structure consisted of porous carbon nanosheets (100-200 nm), ultra-high specific surface area (3402.68 m2/g), and well-developed hierarchical porous structure, which offers a great deal of adsorption sites and transport channels to dye molecules. The adsorption process of all the dyes onto CAC is better described by Langmuir isotherm model and pseudo-2nd-order kinetic model. The CAC shows ultra-high adsorption capacity for methylene blue (1283.99 mg/g), rhodamine B (4067.57 mg/g), methyl orange (2666.2 mg/g), and congo red (8920.61 mg/g), with an extremely low equilibrium adsorption time (∼10 min). Collectively, this study demonstrated the potential of converting waste cork into high value-added adsorbent for the efficient purification of dye wastewater.

Honeycomb-like activated carbon with microporous nanosheets structure prepared from waste biomass cork for highly efficient dye wastewater treatment.

Cork, a porous biomass material, is consist of thin-walled hollow prismatic cells arranged into a compact and orderly honeycomb-like structure and could be applied as an adsorption material. Here, cork-activated carbons (CACs) with a fluffy honeycomb-like structure were synthesized by two-step pyrolysis with solid KOH chemical activation to rapidly and efficiently adsorb methylene blue (MB) (maximum wavelength: 664 nm). The structure, morphology and surface functional groups of the CACs were characterized using BET, SEM, and FTIR analysis. The results show that the CACs have a well-developed hierarchical porous structure and an ultra-high specific surface area of 2864.9 m2/g, which would facilitate the efficient diffusion and adsorption of MB molecules onto CACs. MB adsorption performance results show that the CACs have an outstanding maximum MB adsorption capacity (1103.68 mg/g) and fast adsorption kinetics (800 mg/L, 99.8% in 10 min), indicating that CACs possess significant advantages compared with most other adsorbents previously reported. The adsorption mechanism was studied by various kinetic models, isothermal models and thermodynamic models. Langmuir model is the most adapted to describe the adsorption process, indicating that the MB molecules are uniformly adsorbed on CAC's surface in a single layer. Moreover, MB adsorption by the CACs was an endothermic, spontaneous and randomly increasing adsorption. The regeneration test showed that the uptake of MB onto CACs can still reached 580 mg/g after three adsorption-desorption cycles, demonstrating the excellent reusability of CACs. The continuous adsorption performance of MB onto CACs was evaluated by a packed column test, which further confirmed its potential as an adsorbent for dye wastewater purification.

Converting industrial waste cork to biochar as Cu (II) adsorbent via slow pyrolysis.

Cork is light, porous, carbon-rich, and renewable, which leads to competitive advantages in the preparation of biochar, as compared to other biomass material. In this work, we propose to convert cork powder into cork-based biochar as Cu (II) adsorbent via slow pyrolysis, thereby providing a reliable and simple method for recycling cork industrial waste. The physicochemical properties of cork-based biochar prepared under different pyrolysis temperatures (450, 550, 650, and 750 °C) and pyrolysis time (0.5, 1.0, 1.5, and 2.0 h) were characterized by elemental analysis, FT-IR, XRD, N2 adsorption and SEM. The adsorption capacity of cork-based biochar on heavy metal ions was further evaluated by Cu ion adsorption testing. Results showed that the cork-based biochar produced under conditions of higher pyrolysis temperature and time, has higher aromaticity and lower polarity, larger specific surface area, and enhanced Cu ion adsorption capacity. The maximum specific surface area of cork-based biochar prepared at 750 °C for 0.5 h was 392.5 m2/g, which surpasses most other biochars reported in previous studies, which are beneficial to the application of wastewater management. The SEM image demonstrated that the biochar retains the special hollow polyhedral cell structure of raw material cork. Furthermore, a large number of pores formed on the cell wall after high temperature pyrolysis, and the cells are connected with each other through these open pores. Finally, cork-based biochar exhibits superior Cu ion adsorption capacity (18.5 mg/g) with a shorter equilibrium time (4 h), which gives it a competitive advantage to similar adsorbents.