Mohammad I. El-Khaiary

MALACHITE GREEN ADSORPTION BY RATTAN SAWDUST: ISOTHERM, KINETIC AND MECHANISM MODELING

In this work, the adsorption of malachite green (MG) on rattan sawdust (RSD) was studied at 30 degrees C. The results indicated that RSD can be used as a low-cost adsorbent for the removal of MG dye from aqueous solutions. Equilibrium data were analyzed by two isotherms, namely the Freundlich isotherm and the Langmuir isotherm. The best fit to the data was obtained with the Langmuir isotherm. The monolayer adsorption capacity of RSD was found to be 62.71 mg/g. The adsorption kinetics can be predicted by the pseudo-first-order model. The mechanism of adsorption was also studied. It was found that for a short time period the rate of adsorption is controlled by film diffusion. However, at longer adsorption times, pore-diffusion controls the rate of adsorption. The amount adsorbed on the outer surface was estimated from the time where film-diffusion stops controlling the adsorption rate.

Equilibrium, kinetics and mechanism of malachite green adsorption on activated carbon prepared from bamboo by K2CO3 activation and subsequent gasification with CO2

In this work, the adsorption of malachite green (MG) was studied on activated carbon prepared from bamboo by chemical activation with K(2)CO(3) and physical activation with CO(2) (BAC). Adsorption studies were conducted in the range of 25-300 mg/L initial MG concentration and at temperature of 30 degrees C. The experimental data were analyzed by the Freundlich isotherm, the Langmuir isotherm, and the multilayer adsorption isotherm. Equilibrium data fitted well with the Langmuir model with maximum adsorption capacity of 263.58 mg/g. The rates of adsorption were found to confirm to pseudo-second-order kinetics with good correlation and the overall rate of dye uptake was found to be controlled by pore diffusion throughout the entire adsorption period. The results indicate that the BAC could be used to effectively adsorb MG from aqueous solutions.

Removal of basic dye from aqueous medium using a novel agricultural waste material: Pumpkin seed hull

In this work, pumpkin seed hull (PSH), an agricultural solid waste, is proposed as a novel material for the removal of methylene blue (MB) from aqueous solutions. The effects of the initial concentration, agitation time and solution pH were studied in batch experiments at 30 degrees C. The equilibrium process was described well by the multilayer adsorption isotherm. The adsorption kinetics can be predicted by the pseudo-first-order and the modified pseudo-first-order models. The mechanism of adsorption was also studied. It was found that for a short time period the rate of adsorption is controlled by film diffusion. However, at longer adsorption times, pore-diffusion controls the rate of adsorption. Pore diffusion takes place in two distinct regimes, corresponding to diffusion in macro- and mesopores. The results demonstrate that the PSH is very effective in the removal of MB from aqueous solutions.

Least-squares regression of adsorption equilibrium data : Comparing the options

Experimental and simulated adsorption equilibrium data were analyzed by different methods of least-squares regression. The methods used were linear regression, nonlinear regression, and orthogonal distance regression. The results of the regression analysis of the experimental data showed that the different regression methods produced different estimates of the adsorption isotherm parameters, and consequently, different conclusions about the surface properties of the adsorbent and the mechanism of adsorption. A Langmuir-type simulated data set was calculated and several levels of random error were added to the data set. The results of regression analysis of the simulated data set showed that orthogonal distance regression gives the most accurate and efficient estimates of the isotherm parameters. Nonlinear regression and one form of the linearized Langmuir isotherm also gave accurate estimates, but only at low levels of random error.

Methylene blue adsorption by the waste of Abu-Tartour phosphate rock.

Phosphate rock (PR) is an abundant ore and represents the basic raw material for the phosphatic fertilizer industry. Prior to industrial processing, PR is concentrated by grinding-and-screening to separate a fine fraction that is very poor in P(2)O(5). This fine fraction is a solid waste and represents a disposal problem. The present study shows that the fine fraction of ground-and-screened Abu-Tartour PR can be used as an adsorbent for the removal of methylene blue dye from aqueous solutions. The amount of dye adsorbed was found to vary with initial methylene blue concentration and contact time. Raising the temperature enhances the rate of adsorption but has no effect on the adsorption capacity at equilibrium. The adsorption equilibrium data were found to fit the Langmuir isotherm, indicating monolayer adsorption on a homogeneous surface. The Elovich model can be used to predict the adsorption kinetics at ambient temperatures especially when the initial concentration of MB is relatively high, while Hos model deviates from the data as the initial concentration increases. However, as the temperature increases and MB concentration decreases, Hos model fits the data better than the Elovich model. On studying the mechanism of adsorption, the results showed that the overall rate of dye uptake is controlled by intraparticle diffusion. The multilinear plots of intraparticle diffusion were modeled by piecewise linear regression and related to pore-size distribution of the adsorbent.

Adsorption of methylene blue from aqueous solution by chemically treated water hyacinth

Water hyacinth (WH), an aquatic plant macrophyte, was investigated for its ability to perform as a suitable adsorbent for methylene blue (MB) from aqueous solution. The non-living biomass of WH was subjected to several chemical treatments, namely, washing with hot water, washing with hot dilute HCl, soaking in NaOH, soaking in HNO3, and sulfonation. The system variables studied also include pH and MB concentration. The Langmuir isotherm was found to represent the measured adsorption data well except for WH soaked in NaOH, which was found to be better represented by the Freundlich isotherm. Values of the dimensionless separation factor, K R, indicated that the adsorption systems in this study are all favorable. Values of the first layer of adsorption were calculated by the non-linear multilayer adsorption model, and the specific surface area values were found to be high and comparable to commercially activated carbons.

Extraction of Al(iii) from phosphoric acid by HDDNSA

Abstract A study was conducted on the stoichiometry of the complex formed by the extraction of aluminium ions by didodecyl naphthalene sulphonic acid (HDDNSA) from phosphoric acid solutions. The experimental results were analyzed numerically by non-linear regression. It was found that aluminium is extracted in the form of the complex ion Al(DDNSA) 3 . The value of the equilibrium constant of the reaction was also calculated.