Halloysite nanotubes (HNTs) have been proposed as a potential support to immobilize enzymes. Improving enzyme loading on HNTs is critical to their practical applications. Herein, we reported a simple method on the preparation of high-enzyme-loading support by modification with dopamine on the surface of HNTs. The modified HNTs were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy analyses. The results showed that dopamine could self-polymerize to adhere to the surface of HNTs and form a thin active coating. While the prepared hybrid nanotubes were used to immobilize enzyme of laccase, they exhibited high loading ability of 168.8 mg/g support, which was greatly higher than that on the pristine HNTs (11.6 mg/g support). The immobilized laccase could retain more than 90% initial activity after 30 days of storage and the free laccase only 32%. The immobilized laccase could also maintain more than 90% initial activity after five repeated uses. In addition, the immobilized laccase exhibited a rapid degradation rate and high degradation efficiency for removal of phenol compounds. These advantages indicated that the new hybrid material can be used as a low-cost and effective support to immobilize enzymes.

CCS, Carbon Capture and Storage, is considered a promising technology to abate CO2 emissions from point sources. The present review deals with the principle of postcombustion capture techniques, including thermal or pressure swing principles, adsorption or absorption, and electrical swing or membrane separation processes.Opportunities and challenges are assessed. In the first section of absorption processes, several commercial technologies are compared, and complemented by the aqueous or chilled ammonia (NH3) process, and a dual or strong alkali absorption. The second section deals with adsorption where fixed beds, circulating fluidized beds and countercurrent bed configurations will be discussed, with special focus on the different adsorbents ranging from zeolites or activated carbon, to more complex aminefunctionalized adsorbents, nanotubes or metal organic frameworks (MOFs), and alkali-

The peanut shells were transformed into porous carbon with high surface area through a simple ZnCl 2 -molten salt synthesis process. ABSTRACTPreparation of porous carbon with high surface area from biomass is important for its practical application. In the present paper, the peanut shells were transformed into porous carbon through a simple ZnCl 2 -molten salt synthesis (MSS) process. The carbonization and activation two processes could be completed together within one step, and carbonization time and temperature were reduced significantly because of the favorable flux environment for carbonization reaction provided by molten ZnCl 2 medium. The properties of peanut shells activated carbon (PAC) were characterized by XRD, TG-DSC, SEM, TEM, FT-IR spectra and BET isotherms. The results showed that the as-prepared PAC was amorphous and hierarchical porous structure with high surface area of 1642 m 2 /g. Some functional groups could be retained on surface of PAC and provide more absorbing sites for adsorption. While the prepared PAC was used as an adsorbent to remove dye of methylene blue (MB) from aqueous solution, it exhibited superior adsorption capacity as high as 876 mg/g, which indicates that the PAC from peanut shells can be used as a low-cost and effective adsorbent for water purification. pore distribution curve. It is noteworthy that there are three distinct distributions (plateaus), which can be attributed to presence of mesopores with pore radius of 9 nm, 13 nm and 22 nm, respectively. 35 Figure 4. (a) Nitrogen adsorption-desorption isotherms of PAC (b) The corresponding pore size distribution of PAC using DFT method.Figure 5 shows the FT-IR spectra of PAC prepared at pyrolysis temperature of 230 °C and 480 °C. Compared with the PAC pyrolyzed at 230 °C, most functional groups can be remained in the PAC pyrolyzed at 480 °C. In sample PAC at 480 °C, the presence of the bands at 3430 and 1616 cm -1 can be attributed to N-H stretching vibration and N-H in-plane bending vibration, respectively. The peak observed at 2925 cm −1 is conditions, such as adsorbent dose, contact time, temperature and initial concentration.Adsorbent dose is an important parameter for the adsorption process. The effect of the adsorbent dose was investigated by using different amounts of adsorbent (from 0.01 to 0.06 g) in 50 mL 100 mg/L MB aqueous solution at 298 K for 5 h. The result is shown in Figure 6. The result reveals that the removal efficiency increases from 63.98% to 96.97% while the adsorbent dose increases from 0.01 to 0.06 g, which is attributed to that more adsorbents can provide more surface area and absorbing sites for adsorption. However, the adsorption capacity decreases from 458.39 to 120.67 mg/g with the adsorbent dose increasing from 0.01 to 0.06 g. Due to the total treatment cost depending on the cost of the adsorbent, the compromise between removal efficiency and amount of adsorbent should be optimized for the treatment.Consequently, the adsorbent dose of 0.02 g was selected at in the subsequent experiments, which ...

Inorganic nanostructures and their assemblies play important roles in immobilizing biomolecules. Herein, we developed a facile and green methodology to assemble natural halloysite nanotubes (1D building blocks) into nest-like porous microspheres (3D architecture). We further modified the microspheres with dopamine to form a biomimetic entity. The interconnected and hierarchical pores within the microspheres provide larger pore volume to entrap biomolecules, and the abundant functional groups on the pore surface bond covalently with enzyme to enhance the immobilization ability. The porous microspheres showed excellent loading capacity for laccase immobilization as high as 311.2 mg/g, around 30 times higher than the individual halloysite nanotubes (11.3 mg/g). The specific activity above 80% was retained for the immobilized laccase compared to the free laccase. In addition, the immobilized enzyme exhibited remarkable thermal and recycle use stability. The biomimetic microspheres are expected to be biologically safe and chemically stable microcapsules for immobilizing a variety of biomolecules because of their natural and biofriendly characteristics.

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Laccase was immobilized in polyvinyl alcohol beads containing halloysite nanotubes (PVA/HNTs) to improve the stability and reusability of enzyme. The porous structure of PVA/HNTs beads facilitates the entrapment of enzyme and prevents the leaching of immobilized laccase as well. Halloysite nanotubes act as bridge to connect the adjacent pores, facilitating the electron transfer and enhancing the mechanical properties. PVA/HNTs beads have high laccase immobilization capacity (237.02 mg/g) and activity recovery yield (79.15%), indicating it can be used as potential support for laccase immobilization. Compared with free laccase, the immobilized laccase on hybrid beads exhibits enhanced pH tolerance (even at pH 8.0), good thermal stability (57.5% of the initial activity can be maintained at 75 °C), and excellent storage stability (81.17% of enzyme activity could be retained after storage at 4 °C for 5 weeks compared with that for free enzyme of 60%). Also, the removal efficiency for reactive blue can reach as high as 93.41% in the presence of redox mediator 2,2-azinobis(3-ethylbenzthiazoline-6-sulfonate), in which adsorption and degradation exist simultaneously. The remarkable pH tolerance, thermal and storage stability, and reuse ability imply potential application of porous PVA/HNTs immobilized enzyme in environmental fields.

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