Über die Adsorption in Lösungen

Low cost adsorbents for the removal of organic pollutants from wastewater.

A functional hybrid of reduced graphene oxide (RGO)–Fe3O4 nanoparticles (NPs) has been chemically synthesized with exceptionally high yield and tunable RGO/Fe3O4 ratio. The adsorption behaviors of a series of dyes using this hybrid as the adsorbent are systematically investigated in aqueous solutions through real-time monitoring of the fingerprint spectral changes of the dyes. The results show that, benefiting both from the surface property of RGO and from the magnetic property of Fe3O4, the hybrid possesses quite a good (although unoptimized) and versatile adsorption capacity to the dyes under investigation, and can be easily and rapidly extracted from water by magnetic attraction. Most importantly, it is found that by simply annealing in moderate conditions, this hybrid adsorbent can be easily and efficiently regenerated for reuse with hardly any compromise of the adsorption capacity. Furthermore, the adsorbability of this hybrid shows satisfactory tolerance against the variations in both pH environment and dye concentration. Even when exposed to a multi dye cocktail, the hybrid can work well without suppressing the adsorption capacity for each of the dyes, as compared with that measured separately. The inherent advantages of this nanostructured adsorbent, such as non-compromised adsorption capacity, low cost, easy, rapid extraction and regeneration, good tolerance, multiplex adsorbability, and handy operation, may pave a new, efficient and sustainable way towards highly-efficient dye pollutant removal in Earth's water environments.

Highly efficient dye adsorption and removal: a functional hybrid of reduced graphene oxide–Fe3O4 nanoparticles as an easily regenerative adsorbent

Activated carbon derived from finger citron residue (FAC) was tested as a new type of adsorbent for the removal of harmful dyes, namely, the anionic dye methyl orange (MO) and the cationic dye methylene blue (MB), from contaminated water. Liquid-phase adsorption experiments were conducted, and the maximum adsorption capacity was determined. Various conditions were evaluated, including initial dye concentration, adsorbent dosage, contact time, solution pH, and temperature. The Langmuir and Freundlich adsorption models were used to describe the equilibrium isotherm and to calculate the isotherm constants. It was found that the adsorption capacity of FAC is much higher than those of other types of activated carbons. Maximum equilibrium adsorption capacities of 934.58 and 581.40 mg/g for MO and MB, respectively, were achieved. Three simplified kinetic models, namely, pseudo-first-order, pseudo-second-order, and intraparticle diffusion equations, were used to investigate the adsorption process. The pseudo-seco...

Adsorptive Removal of Methyl Orange and Methylene Blue from Aqueous Solution with Finger-Citron-Residue-Based Activated Carbon

The aim of this work is to study the properties of an activated carbon prepared from apricot stones by carbonisation for 1 h at 700 °C and chemical activation with a mixture of H3PO4 + HNO3 and compared to a commercial activated carbon. The adsorbent materials were characterised with FTIR spectroscopy, XRD, SEM/EDX and surface chemistry. The maximum uptake of MB and MO onto the ASAC and CAC under optimised conditions was determined to be 99.5%. The absorption processes of MB and MO by ASAC and CAC were endothermic and exothermic, respectively. Acidic conditions promote the transfer of anionic dye (MO) molecules onto the ASAC and CAC surface by electrostatic attraction. The adsorbents were better able to remove the cationic dye than the anionic dye. The competitive adsorption of dyes favoured the MB on ASAC and CAC in the mixture solution. The Langmuir isotherm model and the pseudo-second order kinetic model were observed to fit the adsorption data well. The mechanism of the adsorption process was determined based on an intraparticle diffusion model. The results of this study will be useful for future scale-up using this apricot stone material as a low-cost adsorbent for the removal of cationic and anionic dyes.

Adsorption of dyes on activated carbon prepared from apricot stones and commercial activated carbon

Adsorption of methyl orange from aqueous solution onto calcined Lapindo volcanic mud.

The impregnation of zinc particles into MFI zeolite (HZSM-5) caused the formation of catalytically active protonic acid sites for isomerizing n-pentane in the presence of hydrogen. An infrared (IR) study with preadsorbed pyridine revealed that these protonic acid sites originated from the spillover of molecular hydrogen from the zinc species onto the zeolite surface. The requirements for this spillover effect were further studied by IR spectroscopy of adsorbed ammonia and carbon monoxide. The presence of zinc species in HZSM-5 suggested the exchange of acidic character towards strong Lewis acids rather than Bronsted acid sites. The isomerization of n-pentane over the Zn/HZSM-5 catalyst resulted in high activity and stability and the conversion to iso-pentane depends on the promotive effect of hydrogen as a carrier gas.

N. Aini M. Razali

Papers

Adsorption of methyl orange from aqueous solution onto calcined Lapindo volcanic mud.

Hydrogen spillover behavior of Zn/HZSM-5 showing catalytically active protonic acid sites in the isomerization of n-pentane

Complete electrochemical dechlorination of chlorobenzenes in the presence of various arene mediators.