Search

A double-pronged approach to pollution management is proposed by sustainably managing solid wastes and converting them to activated carbons that are then utilized for water treatment. In this study, gas-to-liquids (GTL) derived biosolids, carboard and their mixed samples are used to produce the activated carbons. In a laboratory batch study, a Box-Behnken experimental design was used with four factors and three levels to optimize the removal of single component strontium and barium, and the binary system of pollutants from an aqueous solution. The design incorporated response surface modeling (RSM) techniques with a total of 29 different experimental data points collected and analyzed in this study. The study was conducted considering four parameters: the initial pH of the solution (ranging from 4.0 to 8.0), temperature (ranging from 20 to 40 ℃), the percentage of cardboard (fixed at 0 %, 50 %, and 100 %), and the amount of adsorbent (between 0.05 and 0.5 g). These factors were assigned three levels, represented as −1, 0, and 1. A second-order polynomial regression equation was then developed to estimate the responses. The statistical significance of the independent variables and their interactions was assessed using analysis of variance (ANOVA) with a 95 % confidence level (α = 0.05). The results revealed that only temperature and dosage show significant effects on the responses and that optimum values of the selected parameters were obtained by solving the prediction equations, which were validated with less than 4 % error %. In an attempt to optimize the factors, a pH of 5.5, temperature of 40 ℃ and dose of 0.3 g is found for all three samples. Validation results for optimization also proved that varying the percentage cardboard showed little difference in the percentage removal of all the pollutants. The results from this study can be directly applied for any such systems trying to optimize these parameters and the prediction equations can be utilized effectively. [Display omitted] [ABSTRACT FROM AUTHOR]

This work presents the characterization and application of activated carbon (AC) impregnated with different loadings of Fe2 O3 nanoparticles for strontium removal from produced water. The initial strontium concentration, the strontium removal efficiency in aqueous media and the kinetics of strontium removal were analyzed by inductively coupled plasma mass spectrometer (ICP-MS). The characterization was performed using field emission scanning electron microscopy (FE-SEM) and Brunauer–Emmett–Teller (BET) surface analysis. Different experimental parameters such as adsorbent dosage, pH of the solution, agitation speed and contact time, were investigated for their effects on the adsorption of strontium from water. The optimum condition for maximum removal of the solute was observed to be 150 min of contact time with the sorbent, pH 7, 150 mg adsorbent dosage and 400 rpm rotational speed. Also it was observed that surface modification of AC with Fe2 O3 nanoparticles enhanced their adsorption efficiency. AC loaded with 1% Fe2 O3 could remove 93% of strontium while when the nanoparticles loading increased to 10%, the solute was completely removed from water. The results obtained are promising for the use of AC loaded with Fe2 O3 nanoparticles in the pretreatment of produced water before the desalination process. Adsorption can be very efficient with low energy consumption and economic feasibility [ABSTRACT FROM AUTHOR]

In this study, the effects of activation time and temperature, as two of the most prominent parameters affecting the porous structure of the carbonaceous materials, have been evaluated. It has been demonstrated that increasing the activation degree enhances the porous structure of the prepared activated carbons. The Methylene Blue (MB) adsorption capacity of the activated carbon with the highest surface area has been determined to be higher than that of a commercial activated carbon, F400, although the surface areas of these two adsorbents are very close. It has been attributed to the higher “effective” surface area of the former adsorbent and thus accessibility of more pores for dye adsorption. Also, the mechanism of Methylene Blue adsorption by tyre char activated carbon has been elucidated by isotherm modeling. It has been demonstrated that since the exponent of the best-fit isotherm model, Redlich–Peterson, approaches unity, a monolayer dye adsorption on a surface with homogeneous active sites can be assumed. Considering the MB adsorption capacities of the produced activated carbons, the MB molecule size and the effective surface areas of the adsorbents, the MB coverage factors have been calculated and the possible MB adsorption orientation has been proposed and modeled. [ABSTRACT FROM AUTHOR]

Highlights: [•] Fractional Theoretical Capacity measure was proposed for isotherm model selection. [•] Using error analysis statistics alone may lead to wrong isotherm model selection. [•] The sorption system for all dyes was heterogeneous based on the Toth model. [•] Fractal dimension can be determined based on the theoretical sorption capacity. [•] The sorbent (GAC) surface was smooth according to the fractal dimension parameter. [Copyright &y& Elsevier]

A comparison of chi-square (X²) and Log-likelihood (G²) statistics of 19 adsorption isotherm models--seven two-parameter models (Langmuir, Freundlich, Dubinin-Radushkevich, Tem- kin, Jovanovic, Harkins-Jura and Halsey) and 12 three-parameter models (Koble-Corrigan, Langmuir-Freundlich, Toth, Redlich-Peterson, Radke-Prausnitz (three models), Fritz-Schlun- der, Jossens, Khan, UNILAN, Vieth-Sladek) have been applied to the experiment of two dyes (Acid Blue 113, Acid Black 1) sorption onto Granular PineCone derived Activated Carbon (GPAC) and three dyes (Acid Blue 80, Acid Red 114, Acid Yellow 117) sorption onto Granular Activated Carbon type Filtrasorb 400 (GAC F400). The study has focused on the assessment of the adequacy and goodness of the fitted models, using two well-known--X² and G²--statistics. The results showed that G² could be better than X² statistic when the number of model parameters is three. [ABSTRACT FROM AUTHOR]

In this study, graphene oxide (GO) was synthesized using Hummers method. The synthesized GO was characterized using field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Fourier transformed infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller (BET) nitrogen adsorption. The analyses confirmed the presence of oxygen functional groups (C=O and C-O-C) on the GO surface. These oxygen functional groups act as active sites in the adsorption Sr (II). The BET analysis revealed the surface area of GO of 232 m2/g with a pore volume of 0.40 cm3/g. The synthesized GO was used as an adsorbent for removing Sr (II) from aqueous solutions. The adsorption equilibrium and kinetic results were consistent with the Langmuir isotherm model and the pseudo-second-order kinetic model. A maximum strontium adsorption capacity of 131.4 mg/g was achieved. The results show that the GO has an excellent adsorption capability for removing Sr (II) from aqueous solutions and potential use in wastewater treatment applications. [ABSTRACT FROM AUTHOR]

The fixed-bed adsorption of acid dyes onto granular activated carbon (Chemviron Filtrasorb 400) has been studied using a homogeneous surface diffusion model (HSDM). The model incorporates the external boundary layer mass transport and homogeneous diffusion inside the particle. A new orthogonal collocation method has been developed and used to solve the diffusion equations. This orthogonal collocation gives a faster solution method compared with the numerical Crank--Nicolson method. The surface diffusivity has been determined by an optimization procedure with minimization of sum of the error squared. The equilibrium relationship between the liquid-phase concentration and the solid-phase concentration has been described by the Redlich--Peterson isotherm. A solid-phase concentration-dependent surface diffusivity was introduced. The Darken model with the Redlich--Peterson isotherm was found to be a suitable correlation model for the adsorption of the acid dyes on carbon. The magnitude of the averaged Ds0 of each dye is in the order of AR114 > AB80 > AY117, which implies that, under the same solid-phase concentration gradient, the rate of mass transport diffusion is higher in AR114 than that in AB80 and AY117. This phenomenon may be explained by the different mobilities of the dye molecules present in the solution by the different arrangements of two sulfonic acid groups in the dye structures. [ABSTRACT FROM AUTHOR]

Abstract: The adsorption of two acid dyes Acid Black 1 (AB1) and Acid Blue 113 (AB113) onto mesoporous granular pine-cone derived activated carbon and the adsorption of three acid dyes Acid Black 80 (AB80), Acid Red 114 (AR114) and Acid Yellow 117 (AY117) onto microporous Granular Activated Carbon (GAC) type F400, from aqueous solution, has been studied in a batch system. Seven two-parameter isotherm models – Langmuir, Freundlich, Dubinin–Radushkevich, Temkin, Halsey, Jovanovic and Harkins–Jura – were used to correlate the experimental data. Adsorption isotherm modeling shows that the interaction of dye with activated carbon surface is by localized monolayer adsorption. In order to determine the best fit isotherm for each system, nine error analysis methods, namely, chi-square (χ 2), log-likelihood (G 2), residual root mean square error (RMSE), sum of the squares of the errors (ERRSQ), composite functional error (HYBRD), derivative of Marquardt''s percent standard deviation (MPSD), average relative error (ARE), sum of absolute error (EABS) and average percentage error (APE) were used to evaluate the data. In order to facilitate decision making for the best fit data set, a procedure of normalizing and combining the error results was adopted producing a “sum of the normalized errors” for each parameter set from which the “lowest normalized error set” is selected. [Copyright &y& Elsevier]

Abstract: The adsorption of a large reactive dye, Reactive Black 5, onto four adsorbents has been studied. A commercial active carbon, F400, was selected as a standard and two active carbons prepared from bamboo, a biomaterial. The two bamboo derived carbons, BACX2 and BACX6 had high specific surface areas, namely, 2123 and 1400m2/g, respectively. A fourth widely used adsorbent, bone char, was also tested. The adsorption capacities for F400, bone char, BACX2 and BACX6 were 198, 160, 286 and 473mg/g, respectively. A series of batch kinetics were carried out to investigate the rate and possible mechanism of Reactive Black 5 adsorption. Two pseudo-kinetic models and one intraparticle diffusion model were tested. The experimental concentration versus time decay curves were best explained by the intraparticle diffusion model. [Copyright &y& Elsevier]

The adsorption of three acid dyes onto activated carbon has been studied. Three single, three binary and one ternary systems have been investigated and both equilibrium and kinetic studies have been determined. The equilibrium capacities based on the Langmuir analysis are 0.253, 0.125 and 0.219 mmol g-1 carbon for Acid Blue 80, Acid Red 114 and Acid Yellow 117, respectively. The batch adsorber rate data for the seven systems have been analysed based on an intraparticle diffusion rate parameter derived from the plots of dye adsorbed versus the square root of time. The data indicate the adsorption mechanism is predominantly intraparticle diffusion. The multicomponent system rate parameters have been correlated with the single component rate parameters by the use of the Langmuir equilibrium parameters. [Copyright &y& Elsevier]

In the last decades, phosphate is considered the main cause of eutrophication and has received substantial attention from the scientific community. Phosphate is a major pollutant that deteriorates water quality, which has been increasing in water resources, primarily due to the increasing global population and corresponding activities. Adsorption technology is amongst the different technologies used to decrease the phosphate levels in water, and has been found to be highly effective even at low phosphate concentrations. Carbonaceous materials and their composites have been widely used for phosphate removal due to their exceptional surface properties and high phosphate sorption capacity. Considering the importance of the topic, this study reviews the reported literature in the field of adsorptive removal of phosphate over various carbon-based adsorbents such as activated carbon, charcoal, graphene, graphene oxide, graphite and carbon nanotubes. Moreover, insights into the adsorption behaviour, experimental parameters, mechanisms, thermodynamics, effect of coexisting ions and the possible desorption processes of phosphate onto modified and unmodified carbonaceous adsorbents are also considered. Finally, research challenges and gaps have been highlighted. [Display omitted] • Review of the literature of phosphate adsorptive removal by carbon based materials. • Adsorption mechanisms, thermodynamics and desorption studies were considered. • Metals impregnation has significantly increases the phosphate sorption capacity. • Knowledge gaps of phosphate removal by carbonaceous adsorbents were outlined. [ABSTRACT FROM AUTHOR]

Due to serious public health threats resulting from mercury pollution and its rapid distribution in our food chain through the contamination of water bodies, stringent regulations have been enacted on mercury-laden wastewater discharge. Activated carbons have been widely used in the removal of mercuric ions from aqueous effluents. The surface and textural characteristics of activated carbons are the two decisive factors in their efficiency in mercury removal from wastewater. Herein, the structural properties and binding affinity of mercuric ions from effluents have been presented. Also, specific attention has been directed to the effect of sulfur-containing functional moieties on enhancing the mercury adsorption. It has been demonstrated that surface area, pore size, pore size distribution and surface functional groups should collectively be taken into consideration in designing the optimal mercury removal process. Moreover, the mercury adsorption mechanism has been addressed using equilibrium adsorption isotherm, thermodynamic and kinetic studies. Further recommendations have been proposed with the aim of increasing the mercury removal efficiency using carbon activation processes with lower energy input, while achieving similar or even higher efficiencies. [ABSTRACT FROM AUTHOR]

Sludge, a byproduct produced from numerous industrial activities, has been recognized as an ecological burden for the society. However, viewing the sludge, as a carbon-rich material, has stimulated new gateways for the production of porous activated carbons for water treatment applications. Herein, various textural properties of the sludge-based activated carbons have been compiled and critically reviewed with the focus on surface area, pore size and pore size distribution for both physically and chemically activated carbons. It has been found that chemical activation using various activating agents yields more superior adsorbents with high specific surface areas than physical activation methods. Moreover, the potential of sludge-derived activated carbons for the sequestration of metals and dyes from aqueous media has been discussed. Furthermore, the adsorption mechanism in several adsorbent–adsorbate systems and the effect of various parameters on the adsorption behavior of different dyes and metals on sludge-based activated carbons have been reviewed. It has been shown that the pollutant uptake capacities of the adsorbents derived from sewage sludge are not only governed by the textural properties of the adsorbents, but also by their surface properties, such as the functional groups and the surface charge and thus it is proposed that both of these crucial factors be considered concurrently. [ABSTRACT FROM AUTHOR]

Abstract: Novel Fe loaded activated carbons have been prepared from sugar beet pulp (BP) agricultural residues by direct steam activation followed by iron impregnation with or without previous oxidation. The corresponding activated carbons were: BP–H2O, BP–H2O–Fe, BP–H2O–H2O2–Fe and BP–H2O–MnO2–Fe. The textural characterization of these tailored activated carbons was based on nitrogen adsorption/desorption isotherms leading to BET surface area values between 741 and 821m2/g and total porous volumes between 0.58 and 0.79cm3/g. Elemental analysis and ash content showed that carbon content reached 78% for BP–H2O with 13.6% of ash and decreased to 50% in iron-based materials. BP–H2O and BP–H2O–Fe revealed a basic nature with pHPZC values of 9.8 and 9 respectively while BP–H2O–H2O2–Fe and BP–H2O–MnO2–Fe had acid pHPZC (5.1 and 3.6). Their surface chemistry has been investigated by XPS analysis and by the quantification of the surface chemical moieties based on Boehm’s approach. A clear relationship was found between the surface iron content and the strong acidic groups. Arsenic (As(V)) adsorption isotherms were performed and Langmuir, Freundlich, Redlich–Peterson models were used to describe the experimental data by non-linear regression. It was found that Redlich–Peterson isotherm provided the best fit and the Langmuir adsorption capacities confirmed that the iron-based activated carbons were highly attractive for As(V) removal with capacities up to 17mgg−1. Finally, it has been shown that the surface iron content determined by XPS analysis is very well correlated with Langmuir qm values (r 2 =0.982) and with the strong acidic moieties deduced from the Boehm’s method. [Copyright &y& Elsevier]

Abstract: A series of activated carbons were prepared from bamboo by chemical activation with HCl, HNO3 and H2SO4. Unlike phosphoric acid, these three acids are not commonly used as an activating agent for lignocellulosic materials. The effect of operating variables such as activation temperature, impregnation ratio (the mass ratio between bamboo/acid) and holding time were investigated. The resultant carbons were evaluated for the yield, surface area, pore size distribution, pH, elemental composition and ash. At an impregnation ratio (the mass ratio between bamboo/acid) of 1, activated carbon with BET surface area and micropore volume as high as 553m2/g and 0.239cc/g was obtained at 1173K using H2SO4 as an activating agent. Lower impregnation ratio and shorter holding time were favourable to the yield and surface area while increasing impregnation ratio enhanced mesoporosity of the carbons. This can be attributed to the transformation of micro- to mesopores in the presence of higher ‘basic’ element contents such as nitrogen and sulphur. [ABSTRACT FROM AUTHOR]

Abstract: Two types of activated carbons from tyre char (with or without sulphuric acid treatment) were produced via carbon dioxide activation with BET surface areas in the range 59–1118m2/g. Other characterisation tests include micropore and mesopore surface areas and volumes, pH, and elemental compositions, particularly heteroatoms such as nitrogen and sulphur. They were correlated to the adsorption capacity which were in the range of 0.45–0.71mmol/g (untreated) and 0.62–0.84mmol/g (acid-treated) for Acid Blue 25. In the case of larger-sized molecules like Acid Yellow 117, capacities were in the range of 0.23–0.42mmol/g (untreated) and 0.29–0.40mmol/g (acid-treated). Some tyre carbons exhibit a more superior performance than a microporous, commercial activated carbon (Calgon® F400). By modelling the dye adsorption equilibrium data, the Redlich–Peterson isotherm is adopted as it has the lowest SSE. Based on the surface coverage analysis, a novel molecular orientation modelling of adsorbed dyes has been proposed and correlated with surface area and surface charge. For the acid dyes used in this study, molecules were likely to be adsorbed by the mesopore areas. [Copyright &y& Elsevier]

Abstract: The disposal of waste tyre represents a serious concern in environmental management. Owing to the high carbon content of waste tyre rubber, it is feasible to convert waste tyres to a value-added product, i.e. activated carbon, for environmental applications. This study focuses on the effect of different activation conditions (e.g. temperature, holding time and acid treatment) on the porosity of activated carbons produced from tyre rubber. Experimental studies showed that nitric acid treatment to tyre chars is able to remove certain mineral contents such as Ca, K and Na, which affect the reactivity of gas–solid reactions in the subsequent physical activation process (CO2 as activating agent). Those acid-treated carbons developed high surface areas (over 1000m2/g) that were comparable to commercial products. They also posses high mesopore volume up to 0.855cc/g which has been shown favourable to the adsorption of larger-sized dye molecules. The Redlich–Peterson equilibrium isotherm model yielded the best-fit to experimental data for all three dyes using the non-linear error functions. [Copyright &y& Elsevier]