Textural Properties Of Activated Carbons Research Articles

Low-cost activated carbon preparation from Corn stigmata fibers chemically activated using H3PO4, ZnCl2 and KOH: Study of methylene blue adsorption, stochastic isotherm and fractal kinetic

The aim of this study was to produce a low-cost activated carbon (AC) from an inexpensive precursor material, corn stigmata (CS), by chemical activation at low temperatures using H3PO4, ZnCl2 and KOH. The results were showed that activation with phosphoric acid provides an adsorbent with a larger specific surface area (SBET) and high pore size. Textural and physicochemical properties of ACs activated with H3PO4 were then studied in different activation temperature. The increase of activation temperature from 200° to 500°C allows the development of many surface functions and the development of a mixture of meso and microporosity, so the SBET increase from 0.25 to 820 m2/g. The physicochemical and textural properties of ACs were analyzed by N2 adsorption–desorption, FTIR, Boehm’s titration, point of zero charge (pHPZC), SEM and EDX.The kinetics and isotherm of methylene blue (MB) adsorption were well described by BSf and GBS models indicating the stochastic and fractal adsorption process and a highly heterogeneous AC surface. The maximum adsorption capacity toward MB, 330.5 mg/g, was high compared to many other results found in literature.

Preparation and characterization of cattle manure-based activated carbon for hydrogen sulfide removal at room temperature

The presence of H2S limits the use of biogas. Activated carbons (ACs) provide economic and environmental advantages with a high removal efficiency for biogas purification compared to other H2S adsorbents. In this study, ACs were prepared by steam and an increased flow of CO2 activation from dairy cattle manure at 850 ℃ and applied to remove H2S at room temperature. The H2S breakthrough capacities were evaluated using a lab-designed test. The compositional and textural properties of ACs were characterized by nitrogen adsorption, FTIR, TGA-MS, SEM and X-ray photoelectron spectroscopy (XPS) techniques before and after H2S adsorption. The 2D-NLDFT model was applied for pore size distribution. Additionally, the manufacturing cost of the best AC was estimated. The results showed that all ACs are microporous carbons with pore widths of 0.67~0.690.67–0.69 nm. The ACs prepared by CO2 activations exhibit better H2S removal performance than those activated with steam. AC4 activated by CO2 with a flow of 1000 ml/m has the largest BET surface area of 408.36 m2/g and the highest H2S breakthrough capacity of 868.45 mg/g. The micropore volume and basic surface pH play a crucial role in H2S removal, and the self-catalytic role of intrinsic sulfur on AC4 may also contribute to the oxidation of H2S. The characterization results indicate that the H2S is oxidized to elemental sulfur, sulfates/sulfuric acid and sulfites/sulfonic acids in the presence of O2 during the adsorption process. Due to the higher efficiency in removing H2S and a total feasible manufacturing cost of $1.05 per kg, AC4 can be considered a cost-effective and promising alternative for biogas desulfurization.

The adsorption kinetics of sodium dodecylbenzenesulfonate on activated carbon. Branched-pore diffusional model revisited and comparison with other diffusional models

The adsorption rate of sodium dodecylbenzenesulfonate (SDBS) on three commercial activated carbons (ACs) and an AC synthesized from almond shells was investigated in this study. The mechanisms controlling the overall adsorption rate of SDBS on ACs were found out by using the pore volume and surface diffusion model (PVSDM). The PVSDM showed that the intraparticle diffusion of SDBS in all ACs was mainly attributed to pore volume diffusion and surface diffusion. The surface diffusion coefficient, Ds, in all samples of ACs are influenced by the amount of surfactant adsorbed at equilibrium, qe, as well as the mean micropore width, L0. The contribution of surface diffusion to the overall intraparticle diffusion ranged from 45 to 70%, depending on the properties of AC. Moreover, the branched-pore diffusional model was revisited (BPDMR) assuming that the Fick diffusion is the only diffusion mechanism in the macropores and the diffusion in the micropores was represented by the micropore rate coefficient, KC. Besides, it was proposed that the parameter f representing the mass fraction of SDBS adsorbed on macropores, can be estimated from the textural properties of ACs. Three new strategies were proposed to analyze the experimental data using BPDMR model, and it was demonstrated that the macropore diffusivity in BPDMR is close to the molecular diffusivity of SDBS in water solution. The micropore rate constant, KC, ranged from 3.90 × 10−6 to 10.6 × 10−6 s−1 and was affected by textural characteristics of ACs. Both models predicted the global adsorption rate of SDBS on ACs satisfactorily.

Tailored activated carbons as catalysts in biodecolourisation of textile azo dyes

Anaerobic reduction of two textile azo dyes (Orange II and Reactive Black 5) was investigated in upflow stirred packed-bed reactors (USPBRs) with biological activated carbon (BAC) system. The bioreactors were prepared with tailored activated carbons (ACs) having different textural properties and various surface chemistries. A kinetic model proposed previously was able to describe the catalytic azo reduction in all cases. Decolourisation with very high reduction rates took place in the case of each AC. Best dye removals were ensured by the AC having the highest surface area: conversion values above 88% were achieved in the case of both azo dyes at a space time of 0.23min or higher, corresponding to a very short hydraulic residence time of about 0.30min at the most. The decolourisation rates were found to be significantly influenced by the textural properties of AC and moderately affected by its surface chemistry. The results confirmed the catalytic effects of carbonyl/quinone sites and, in addition, delocalized π-electrons seemed to play a role in the catalytic reduction in the absence of surface oxygen groups.