Typical Sorbent Research Articles

Zirconium-based nanoclusters as molecular robots for water decontamination

Water contamination owing to anionic pollutants is a persisting and ubiquitous global threat. The current remediation technologies are mostly low in efficiency, expensive in materials and often associated with complicated processes. Herein, we report a characteristic zirconium-based nanocluster that can work as molecular robots for the efficient remediation of anions-contaminated water with great effectiveness and molecular-level accuracy. It exhibits a stimuli-responsive behavior to facilitate the water treatment process: dissolve in acidic aqueous solutions for molecular-level decontamination and quickly aggregate for post-remediation collection. It can precisely capture the representative anionic pollutants, whilst featuring satisfactory capacities (ca. 175 mg-arsenic/g, 60 mg-chromium/g, 45 mg-fluoride/g, 70 mg-phosphorus/g, respectively), super-fast kinetics (finishing uptake within seconds, which is two to four orders of magnitude faster than typical sorbents), as well as multi-cycle applications without appreciable loss of activity. The coexisting common ions show no effect on the target uptake. The responsible active site investigation shows that four active sites are responsible for the monovalent pollutant removal, and the active sites work in pairs to capture divalent chromate species. Cost analysis shows its economical applicability in practical applications. This work would lead to the development of effective water decontamination with higher effectiveness, more convenience, lower cost and more practical application value.

Hollow polyethyleneimine/carboxymethyl cellulose beads with abundant and accessible sorption sites for ultra-efficient chromium (VI) and phosphate removal

• Novel hollow beads with abundantly accessible sorption sites were prepared. • Demonstration of excellent removal capability of hexavalent chromium and phosphate. • Excellent adsorption and recycling performance for two anionic pollutants. • Easy-to-handle preparation and recovery. Novel millimeter-scale hollow polyethyleneimine/carboxymethylcellulose beads were facilely prepared by simply adjusting the usage of polyethyleneimine for surface modification of preformed solid carboxymethylcellulose beads, which were gradually transformed into hollow beads during the glutaraldehyde mediated cross-linking process. Taking advantage of the hollow structure and porous shells which possess abundant, accessible sorption sites, this newly designed bead-like sorbent exhibited very high adsorption capacity for Cr(VI) and phosphates, for which the exceptional value of 535.39 mg/g and 150.65 mg/g was achieved under fitting conditions, respectively, and both of them much superior to most reported studies. Most importantly, the adsorption capacity for Cr(VI) and phosphate over the typical sorbent remained at high levels even after 6 and 22 cycles, respectively, which is another feature of the hollow bead-like sorbent. Based on various characterization results like SEM-EDX, FT-IR, TGA, zeta potential, XPS, etc., it showed that the adsorption mechanism of Cr(VI) over as-fabricated hollow bead-like sorbents could be mainly correlated to the electrostatic attraction and reduction manner, while the adsorption process of phosphate was mainly due to the electrostatic interaction. By its millimeter-sized shape with surface accessible sorption sites, the column adsorption testing revealed that the Thomas model fitted well with the phosphate adsorption process. Given its controllable fabrication process, excellent adsorption performance, and exceptional mechanical properties, this newly designed millimeter-scale hollow bead-like sorbent has promising applications in the field of anionic pollutant removal.

A sorbent-focused techno-economic analysis of direct air capture

Direct air capture, the removal of carbon dioxide from air, requires special sorbents, with high capture capacity, fast kinetics and long lifetime. Beyond that they also need to be affordable. However, since air capture is still in an early development stage, costs are still uncertain.We present a techno-economic model to value a sorbent based on the CO2 market price and the most important sorbent characteristics: cycle time, loading capacity, and rate of degradation. The model gives a net present value equation for any air capture sorbent, whether it uses a moisture swing, pressure swing or thermal swing for regeneration and makes it possible to estimate the maximum allowable budget for any air capture sorbent, i.e., the sorbent value.The analysis aims to focus the rapidly growing field of air capture sorbent development onto the most important parameters. The value of a sorbent is dramatically affected by its longevity. To be economically viable, the typical sorbent must survive tens if not hundreds of thousands of loading and unloading cycles. The model can also be used to investigate the interactions between different sorbent parameters. For example, the correlation between loading capacity and cycle time makes it possible to determine the cycle time that optimizes the economics of an air capture device.Our analysis highlights the significance of some neglected parameters in air capture cost analysis such as cycle duration and stability of the sorbent. Finally, the analysis can also be adapted to post-combustion flue gas sorbents.

Creviced titanate nanotube modified with stearyl trimethyl ammonium bromide as a support for amine-based CO2 sorbent

In this paper, a series of protonated titanate nanotubes (PTNTs) modified by stearyl trimethyl ammonium bromide (STAB) were prepared as supports for Polyethyleneimine (PEI)-based sorbents. The CO2 adsorption performance was evaluated in a self-assembled fixed bed reactor. The typical sorbents were characterized by XRD, EDS, SEM, HR-TEM, N2 adsorption-desorption, FT-IR and TGA. Results indicate that the modification significantly improves CO2 adsorption capacity of the sorbents. The maximum CO2 adsorption amount of 2.22 mmol/g was obtained over the modified PEI-based sorbent in 2% CO2/air. Based on the characteristic analysis, the formation of creviced nanotubes, instead of intact nanotubes, is testified because of the modification. Such unique nanotubes possess the higher BET surface area and larger pore volume, which enables more PEI to uniformly distribute on the surface of modified PTNT supports. Especially, it is easier for PEI to enter the inner pores through the crevice than from tube orifices, avoiding pore blockage and facilitating CO2 diffusion in pores. The abundant amine-sites and small internal diffusion resistance endow the modified sorbent with large CO2 adsorption capacity. In addition, the PEI/PTNT adsorbent displays good thermal stability and reusability.

Extraction of phenols from aqueous solutions by β-cyclodextrin polymers. Comparison of sorptive capacities with other sorbents

The removal of phenols from aqueous solutions by crosslinked β-cyclodextrin polymers has been studied. For cresols, the position of the methyl group influences the interaction with cyclodextrin polymers crosslinked with epichlorohydrin, being p-cresol the most adsorbed one. The isosteric heat of adsorption is almost constant with the surface coverage in the case of phenol, but varies for the cresols. When compared with other typical sorbents used to extract phenol from water (activated carbon, the macroporous resin Lewatit OC 1064, and calcium alginate), cyclodextrin polymers crosslinked with different reagents (epichlorohydrin, succinyl chloride and two diisocyanates) show high sorption capacities, especially at high phenol concentrations.

Carbon-mineral adsorbents — new type of sorbents? Part I. The methods of preparation

The methods of preparation of carbon-mineral adsorbents produced on the basis of typical sorbents (e.g. silica gels, alumina, titanum oxide, Celite 545) and other sorbents important in industry (mainly aluminosilicates and natural silicates) are described. Among the methods of preparation have been distinguished mechanical mixing, incorporation, carburization of organic substances bonded chemically or physically with the surface of mineral adsorbent, as well as deposition of the carbon on catalyst and adsorbent surfaces during different adsorption and catalysis processes. The source of starting materials for preparation of complex adsorbents has been shown. The thermodynamic bases of the process of formation of carbon deposits are also discussed.