Adsorption of p-nitrophenol from aqueous solutions onto activated carbon fiber

Tang, Dengyong; Zhang, Zheng; Lin, Kui; Luan, Jingfei; Zhang, Jibiao

doi:10.1016/j.jhazmat.2006.08.066

Cited by 192 publications

(95 citation statements)

References 39 publications

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“…The amounts adsorbed of PNP rose with the decrease of the temperature, indicating the apparent exothermic nature of the entire process. Similar effect has been reported by other authors [6,[22][23][24]. In general, physical adsorption processes are typically exothermic; an increase in temperature causes a reaction in the opposite direction, i.e., this produces desorption of molecules from the less energetic active centres, resulting a displacement in the equilibrium toward the fluid phase.…”

Section: Effect Of the Temperature On Adsorptionsupporting

confidence: 86%

Adsorbent ability of lignin-based activated carbons for the removal of p-nitrophenol from aqueous solutions

Cotoruelo

Marques

Díaz

et al. 2012

Chemical Engineering Journal

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a b s t r a c tThis paper reports the p-nitrophenol (PNP) removal from aqueous solutions by adsorption onto active carbons (ACs). Nine ACs were prepared from acid-precipitated eucalyptus kraft lignin following a twostep process consisting in CO 2 partial gasification (750-850• C) after carbonization (350-800 • C) in N 2 atmosphere. The amount adsorbed ranged from 1 to 4.4 mmol/g, and it is related to the initial concentration of adsorbate, temperature, pH, burn off of the activated carbons, and contact time. The equilibrium results were fitted by the Temkin, Dubinin-Radushkevich, and Guggenheim-Anderson-de Boer equations. The main thermodynamic magnitudes were estimated as well, and their values indicated that the adsorption processes were spontaneous and exothermic. The kinetic study showed that the processes are of apparent second order related to the concentrations of the empty active sites on the ACs surface. The values of the effective diffusivities have been calculated and they have suggested that the internal diffusion controls the net mass transfer. The results obtained in the present work can be for the benefit of the preparation of new adsorbents, as well as the primary design of the adsorption equipment with separation or environmental purposes.

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Section: Effect Of the Temperature On Adsorptionsupporting

confidence: 86%

Adsorbent ability of lignin-based activated carbons for the removal of p-nitrophenol from aqueous solutions

Cotoruelo

Marques

Díaz

et al. 2012

Chemical Engineering Journal

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“…However, the same spiking assays performed at low pH (pH 6.5 and 5 from acid phosphatase and β-glucosidase activities, respectively) exhibited high PNP retention from 30 % (acid phosphatase determination in PM + B) up to 70 % which is the case of the β-glucosidase determination in CM + B. These results are in agreement with the pH dependence of phenol adsorption efficiency by activated carbon reported by several authors (Ayranci and Duman 2005;Tang et al, 2007), concluding that the absorption efficiency of activated carbon is lower in alkaline solution than neutral or acid solution. An increase in the amount of OH ions in alkaline solution reduces the diffusion of phenol ions due to an electrostatic repulsion of negatively charged site of the sorbent and phenolic ions.…”

Section: Study Of the Pnp Retention On Biochar-blended Compostsupporting

confidence: 91%

“…These hydrolytic enzymes are measured by colorimetric determination of pnitrophenol (PNP) which is formed as the reaction product of hydrolysis of different nitrophenyl derivatives used as a substrate: nitrophenyl-β-d-glucopyranoside (PNG) for β-glucosidase activity, and p-nitrophenyl phosphatase (PNPP) for alkaline and acid phosphatase activities. By contrast, pnitrophenol is a well-known toxic compound in industrial sector, and is treated by absorption on activated carbon (Tang et al, 2007;Ivančev-Tumbas al 2008). Furthermore, some biochar, produced at high temperature, has similar absorption character to activated carbon (Hale et al, 2013) and interferes with the extraction of soluble organic compounds, leading to underestimation of soil microbial activities (Chan et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Methodological interference of biochar in the determination of extracellular enzyme activities in composting samples

et al. 2014

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Abstract. Biochar application has received increasing attention as a means to trap recalcitrant carbon and enhance soil fertility. Hydrolytic enzymatic assays, such as β-glucosidase and phosphatase activities, are used for the assessment of soil quality and composting process, which are based on use of p-nitrophenol (PNP) derivatives as substrate. However, sorption capacity of biochar can interfere with colorimetric determination of the hydrolysed PNP, either by the sorption of the substrate or the reaction product of hydrolysis into biochar surface. The aim of the present work is to study the biochar sorption capacity for PNP in biochar-blended composting mixtures in order to assess its impact on the estimation of the colorimetric-based enzymatic assays. A retention test was conducted by adding a solution of known amounts of PNP in universal buffer solution (pH = 5, 6.5 and 11, corresponding to the β-glucosidase, acid and alkaline phosphatase activity assays, respectively), in samples taken at the initial stage and after maturation stage from four different composting piles (two manure composting piles; PM: poultry manure, CM: cow manure and two other similar piles containing 10 % of additional biochar (PM + B, CM + B)). The results show that biochar-blended composts (PM + B, CM + B) generally exhibited low enzymatic activities, compared to manure compost without biochar (PM, CM). In terms of the difference between the initial and maturation stage of composting process, the PNP retention in biochar was shown higher at maturation stage, caused most probably by an enlarged proportion of biochar inside compost mixture after the selective degradation of easily decomposable organic matter. TThe retention of PNP on biochar was influenced by pH dependency of sorption capacity of biochar and/or PNP solubility, since PNP was more efficiently retained by biochar at low pH values (5 and 6.5) than at high pH values (11).

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“…In this study, the PNP was expected to have been adsorbed within the range of 2 to 6 via several other mechanism such as Van der Waals forces and complex donor-acceptor mechanism. However the PNP was more or less adsorbed at lower pH because it had been deprotonated and considering the fact that the pH of the adsorbents were 7.4 and 7.6 for PAC (after neutralising with NaOH) and CGAC respectively, then there exist an electrostatic repulsion between the adsorbent and the adsorbate at the higher pH range [20,29,30].…”

Section: Effect Of Ph Of the Solutionmentioning

confidence: 99%