Mathematical Modeling of Sorption on Novel Sorbent Materials

<p>The emission of metal ions in the environment has increased in recent times and since metal ions are not biodegradable, they belong to the cumulative toxins. Contamination of the environment with metal ions poses a serious danger to the entire ecosystem, agricultural production, quality of food and water, as well as to the health of humans and animals. This study investigates sorption as one of the processes which can be used for pollutants removal and efficiency of certain sorbent materials. Specifically, we focus on development and validation of non-linear Langmuir model and non-linear Freundlich model. Their application in sorption experiments is examined by applying different error functions and statistical methods which are employed to calculate the error divergence between observed data and predicted data of sorbate-sorbent system. Presented non-linear sorption models are developed by using programming language Fortran, and the data analysis is obtained by using different tools and packages in programming language R. Many authors are using linear sorption models in the way that they would linearize non-linear sorption models. It is evident that linear sorption models are used due to their simplicity in parameters estimation. We use approach of trying different algorithms and tools in programming language R in order to find the best objective function. This study shows that both non-linear Langmuir model and non-linear Freundlich model can be used for experimental data representation. The results also denote that better estimation and the better fit is given by Langmuir model due to divergence in error functions and graphical representation itself. The choice of sorption model has a great influence on the prediction of solute transfer and great care should be taken in selection of convenient approach.</p>

Caffeine vs. carbamazepine as indicators of wastewater pollution in a karst aquifer

This paper presents the analysis of caffeine and carbamazepine transport in the subsurface as a result of wastewater release in the Sorek creek over the outcrops of the carbonate, Yarkon-Taninim, aquifer in Israel. Both caffeine and carbamazepine were used as indicators of sewage contamination in the subsurface. While carbamazepine is considered conservative, caffeine is subject to sorption and degradation. The objective of the study was to quantify differences in their transport under similar conditions in the karst aquifer. Water flow and pollutant transport in a “vadose zone–aquifer” system were simulated by a quasi-3-D dual permeability numerical model. The results of this study show that each of these two pollutants can be considered effective tracers for characterization and assessment of aquifer contamination. Carbamazepine was found to be more suitable for assessing the contamination boundaries, while caffeine can be used as a contaminant tracer only briefly after contamination occurs. In instances where there are low concentrations of carbamazepine which appear as background contamination in an aquifer, caffeine might serve as a better marker for detecting new contamination events, given its temporal nature. The estimated caffeine degradation rate and the distribution coefficient of a linear sorption isotherm were 0.091 d−1 and 0.1 L kg−1, respectively, which imply a high attenuation capacity. The results of the simulation indicate that by the end of the year most of the carbamazepine mass (approximately 95 %) remained in the matrix of the vadose zone, while all of the caffeine was completely degraded a few months after the sewage was discharged.

Caffeine vs Carbamazepine as indicators for wastewater pollution in a karst aquifer

This paper presents the analysis of caffeine and carbamazepine transport in the subsurface during and after sewage discharge in the Sorek creek over outcrops of the Western Mountain Aquifer (Yarkon-Taninim) in Israel. Both caffeine and carbamazepine were used as indicators for sewage contamination in the subsurface. While carbamazepine is considered conservative, caffeine is subject to sorption and degradation. The objective of the study was to quantify differences in their transport under conditions in the carbonate aquifer. A quasi-3D dual permeability numerical model was used to simulate water flow and transport of both pollutants in a vadose zone – aquifer system. The results of this study show that each of these two pollutants can be considered as effective tracers for characterization and assessment of aquifer contamination. Carbamazepine was found to be more suitable to assess the contamination boundaries, while caffeine can be used as a contaminant tracer only briefly after contamination occurred. In instances when there are low concentrations of carbamazepine which appear as background contamination in an aquifer, caffeine might serve as a better marker for detect new contamination events given its temporal nature. The estimated caffeine degradation rate and the distribution coefficient of linear sorption isotherm were 0.091 d−1 and 0.1 L/kg, respectively, which imply a high attenuation capacity. The results of the simulation indicate that around 95 % of carbamazepine mass was retained in the porous matrix of the unsaturated zone by the end of the year, while all of the caffeine was completely degraded a few months after the sewage was discharged.

DEFINING THE TERMS OF WATER DISTRIBUTION IN TEXTILE BY THE PHOTOMETRY METHODS

The work proved computer photometric method for determining the water concentration in the line textile samples. The aim of the article is the testing of computer visualization techniques to determine the sorption characteristics of textile structural components. The main result is the determination of the actual empirical distribution functions in linear liquid samples. For this purpose one of the boundaries of the test material was set in contact with coloured water. Thanks to the diffusion properties of the material, water spread along the sample changing its brightness. Using of visualization enabled to determine the concentration in the textile sample. Experimental regressive dependence of concentration in a sample of different factors was developed. The proposed concentration dependence of the water from the coordinates and time has the form of exponential function. Exponent index is a characteristic feature of this material, which is characterized its absorption properties. Constants that describe the intensity of a linear sorption of the sample of material were defined. The results can be used in predicting of the water distribution and process modeling of discrete material structure.

Sorption and transformation of the reactive tracers resazurin and resorufin in natural river sediments

Resazurin (Raz) and its reaction product resorufin (Rru) have increasingly been used as reactive tracers to quantify metabolic activity and hyporheic exchange in streams. Previous works have indicated that these compounds undergo sorption in stream sediments. We present a series of laboratory column and batch experiments on Raz and Rru transport, sorption, and transformation within sediments with different physicochemical properties under neutral and alkaline conditions. The data of the column experiments were fitted by a model accounting for physical transport, equilibrium and kinetic sorption, and three first-order reactions. The most likely parameters and their uncertainty were determined by a Markov-Chain Monte Carlo approach. Linear and non-linear sorption isotherms of both compounds were obtained by batch experiments. We found that kinetic sorption dominates sorption of both Raz and Rru, with characteristic timescales of sorption in the order of > 80 min. The linear sorption models for both Raz and Rru appeared adequate for concentrations that are typically applied in field-tracer tests. The supposed two-site sorption model helps interpreting transient tracer tests using the Raz–Rru system.

Sorption-desorption isotherms of dyes from aqueous solutions and wastewaters with different sorbent meterials

The ability of activated carbon and different low-cost by-products and waste material as sorbents to remove various reactive dyes from aqueous solutions and wastewaters was investigated. All aqueous dye solutions contained 2,000 mg l-1 NaCl, to mimic real dye wastewater. Batch kinetic and isotherm experiments were conducted to determine the sorption-desorption behavior of the examined dyes from aqueous solutions and wastewaters by different sorbents, including activated carbon, fly ash, bentonite and bleaching earth. The results from the aqueous solutions indicate that the form of the isotherm equation is not necessarily unique for best description of both sorption and desorption data. The values of the isotherm parameters are not the same, indicating a significant hysteresis effect. Of the 9 sorption systems tested, 5 are best described by the Freundlich, 3 by the Langmuir and 1 by the linear sorption model. Of the 7 desorption systems tested, 5 are best described by the Freundlich and 2 by the linear model. In all cases, the sorption capacity for dye removal was higher for activated carbon, followed by fly-ash and then by bentonite.