Commercial Carbon Adsorbent Research Articles

Biomass-derived adsorbents and nanocomposites for wastewater treatment

Newer biomass-derived adsorbents were developed from green pods of Cassia fistula apart from further nano-metal (Cu, Fe oxide, Ni) and acid modifications. The adsorbents were characterized by FE-SEM, HR-TEM, Powder XRD, BET and FTIR analysis. Removal studies on two different dyes, Malachite green and Congo red, revealed a very high adsorption capacity for the removal of malachite green dye, ∼1355 mg/g for Cu-nanocomposite, 661 mg/g for Fe-nanocomposite and 456 mg/g for unmodified adsorbent; also an order of magnitude, 2000% higher than the reported commercial carbon adsorbents. The results clearly highlight utility of bio-nanocomposites for wastewater treatment and dye removal.

Two-Stage Ozonation – Adsorption Purification of Ground Water from Trichloroethylene and Tetrachloroethylene with Application of Commercial Carbon Adsorbents

ABSTRACT The aim of the research is to choose the most efficient adsorbent for two-stage ozone-sorption purification of groundwater containing both trichloroethylene (TCE) and tetrachloroethylene (PCE) between three carbon sorbents produced in Russia (AUT-M, CAUSORB-221, and AG-3). Sorption isotherms of TCE and PCE on AUT-M and CAUSORB-221 at 296 K were fitted by the Freundlich equation. The better TCE and PCE sorption ability of AUT-M in comparison with CAUSORB – 221 and AG-3 was demonstrated. The optimum parameters for ozonation and sorption stages of groundwater purification from TCE and PCE are elucidated using laboratory and pilot-plant scales. Prolonged test of this technology for purification of ground demonstrated that the higher achievable efficiency of destruction with ozone is 94% for TCE and 38% for PCE. Ozonation-sorption treatment of groundwater allows one to achieve TCE and PCE removal efficiency of 96-97% and 92-94% correspondingly. The most efficient carbon sorbent is microporous carbon fiber AUT-M. Using this sorbent, TCE and PCE concentrations in treated water decrease below the MPC level (5 μg/L) adopted in Russia. It is concluded that the combination of ozonation with sorption of residual contaminants by carbon sorbents is a promising way for the purification of waters containing chlorinated contaminants.

A new approach to characterize the nanostructure of activated carbons from mathematical morphology applied to high resolution transmission electron microscopy images

A new characterization method of the nanoporous structure of activated carbons (ACs) is proposed, based on mathematical morphology analysis of high resolution transmission electron microscopy (TEM) images. It produces refined statistics describing the shape, size and orientation of the defective graphene sheets seen edge on as individual fringes on TEM images. It also provides some quantitative information regarding their spatial arrangement. Especially, assemblages composed of 2–4 nearly parallel fringe fragments could be detected, which were relevant of some partial stacking of the defective graphene sheets. Such assemblages were possibly locally oriented along a common direction to form large continuous domains. To prove the ability of the image analysis tool to reveal distinctive features and degrees of disorder of the AC structures, a set of various commercial carbon adsorbents was characterized. The measured effective spaces separating the individual fringes, the stacks and the continuous domains were examined and compared with the porosity data derived from 77K–N2 adsorption isotherms. Consistency between the two sets of data was assessed and interpreted by considering the N2 diffusional limitations resulting from the micropore network connectivity.

Adsorption of methyl tertiary butyl ether on granular zeolites: Batch and column studies

Methyl tertiary butyl ether (MTBE) has been shown to be readily removed from water with powdered zeolites, but the passage of water through fixed-beds of very small powdered zeolites produces high friction losses not encountered in flow through larger sized granular materials. In this study, equilibrium and kinetic adsorption of MTBE onto granular zeolites, a coconut shell granular activated carbon (CS-1240), and a commercial carbon adsorbent (CCA) sample was evaluated. In addition, the effect of natural organic matter (NOM) on MTBE adsorption was evaluated. Batch adsorption experiments determined that ZSM-5 was the most effective granular zeolite for MTBE adsorption. Further equilibrium and kinetic experiments verified that granular ZSM-5 is superior to CS-1240 and CCA in removing MTBE from water. No competitive adsorption effects between NOM and MTBE were observed for adsorption to granular ZSM-5 or CS-1240, however there was competition between NOM and MTBE for adsorption onto the CCA granules. Fixed-bed adsorption experiments for longer run times were performed using granular ZSM-5. The bed depth service time model (BDST) was used to analyze the breakthrough data.

Structured carbon adsorbents from clay, zeolite and mesoporous aluminosilicate templates

Porous carbons templated from inorganic materials such as zeolites and mesoporous molecular sieves received considerable attention in the last decade. In this context, we discuss the effects of different templating structures on the carbons yielded. We describe templating using a commercial cationic clay (Wyoming bentonite), a commercial zeolite (Tosoh H-Beta) and a synthetic mesoporous aluminosilicate (Al-MCM-48), as exemplars of the categories of inorganic templates we have studied. The main carbon precursor used was furfuryl alcohol, complemented in some materials by an additional treatment using propylene carbon vapour deposition. The structures of the templates and carbons were compared using electron microscopy and powder X-ray diffraction. Carbons were further characterised with elemental analysis and nitrogen adsorption. The templating process is more complex than previously reported; the combination of these different techniques enhances the understanding of its mechanisms. A careful study of the synthesised carbons’ pore size distributions using DFT with various pore geometries was carried out and comparison with two commercial carbon adsorbents made, in order to assess the potential of such templated carbons for gas separation and gas storage.

Preparation and characterization of bimodal porous carbons derived from a styrene-divinylbenzene copolymer

A styrene/divinylbenzene copolymer has been used as precursor for making porous carbons with bimodal pore size distributions (i.e., with both microporosity and mesoporosity). Pretreatment of the as-received copolymer by mild oxidation in air, significantly increased the carbon yield after carbonization. Reactivity studies of the polymer-based chars to CO2 clearly show the influences of some important factors such as carbonization temperature, heating rate, soak time on char reactivities. Bimodal porous carbons were prepared by carbonization of the preoxidized styrene/divinylbenzene copolymer in N2, followed by activation in CO2 at different temperatures to different levels of burnoff. The pore structures of the porous carbons produced have been characterized by various techniques such as gas adsorption and mercury porosimetry. The surfaces of the porous carbons produced, and a commercial carbon adsorbent, have been modified with HNO3 and H2O2 treatment at various conditions. Characterization of the surface oxygen functionality, both quantitatively and qualitatively, has been achieved using techniques such as Linear Temperature Programed Desorption (LTPD) and selective neutralization of bases.