Regression models of adsorbing nickel (II) ions by carbon sorbents

The use of inexpensive materials such as sorbents increases the competitive advantages of removing heavy metal ions, including nickel (II) ions, from aqueous solutions and wastewater. Such materials include active carbons – carbon sorbents. The oxidized carbon sorbent AD-05-2 and its original analogue have been used as the object of this research. The oxidation of carbon sorbent AD-05-2 was conducted using a solution of nitric acid and urea following a conventional method. Oxidation resulted in improvement of the textural characteristics of the carbon sorbent. The total pore volume increased, including the volume of micropores, which had a positive effect on the sorption properties of the obtained sample. This article studies the adsorption of nickel (II) ions by the oxidized carbon sorbent AD-05-2 and its original analogue. For both models, the total time of establishing adsorptive equilibrium in the system adsorbate–adsorbent was 4 hours, pH = 9,6, and the range of temperatures – 298–338 K. The obtained experimental data on the nickel (II) ion adsorption are processed in the software package Statgraphics Plus. Adsorption isotherms are described using parabolic regression models, which cover 98.86–99.99% of the experimental data. The adsorption of nickel (II) ions increases with temperature, as indicated by a higher value of the first derivative dA/dCp, apparently, due to accelerated external diffusion. A significant steep rise of the isotherms corresponds to the temperature of 338 K, which indicates the diffusion effect on the adsorption process. The estimates of the accuracy of regression models are provided by the mean square σ and absolute Δ errors. Autocorrelation of experimental data is estimated using Durbin – Watson (DW) test. The obtained regression models can be applied for calculating the optimum parameters of nickel (II) ions’ adsorption from aqueous solutions and process stream using the oxidized carbonic sorbent AD-05-2 and its original analog.

Treatment of textile dyes using advanced oxidative and adsorptive processes individually and combined: study of the operational parameters, kinetic and adsorptive equilibrium

Advanced oxidative processes (AOP) have been consolidated as an efficient treatment technique to degrade persistent contaminants. In addition to them, biosorption also emerges as a technique capable of removing both pollutants and intermediate products generated by other treatments such as AOP. Thus, this work evaluated the degradation and removal of the mixture of dyes Direct Red 23 and Direct Red 227 in aqueous solution (50 mg·L−1 of each). Preliminary tests showed that the photo-Fenton system under sunlight radiation was the most efficient, reaching a degradation ≥93%. For the adsorptive process using chicken eggshell, preliminary tests indicated that the ideal dosage of adsorbent was 8.0 g·L−1. For this process, a factorial design indicated the best working conditions, which demonstrated from the system adjusted well to the Elovich (kinetic) model and to the Freundlich and Sips models (equilibrium). When associating the two processes, AOP followed by adsorption achieved a total degradation/removal of ≈98% (for all λ) in a time of 60 min. Thus, the feasibility of the combined treatment is indicated.

Study on Competitive Sorption Capacity of Sr2+/Cs+ in Zeolite and Palygorskite

Competitive sorption capacity of equal concentration of Cs+ and Sr2+ in zeolite and palygorskite were studied by the intermittence method. zeolite and palygorskite of adsorbed Cs+ and Sr2+ were analysed with the XRD. They could offer some references for the sake of valuing mid-lower radwaste disposition. The results showed that adsorptive equilibrium time of NF to Cs+ and Sr2+ was about seven day, that of ZF was about three day, and that of CA was about fourteen day. Equilibrium adsorptive quantity of ZF to Cs+ and Sr2+ was the best, and that of NF was second, and that of CA was third. Sorption capacity of NF to Cs+ was the better than that to Sr2+, and selection of CA to Cs+ and Sr2+ was the little, and that of ZF was the lest. Equilibrium adsorptive rate of ZF to Sr2+ was almost the 100% and that of ZF to Cs+ was about 71.8% and that of NF to Cs+ was 66% and that of NF to Sr2+ was only 15% and that of CA to Sr2+ was about 28.6% and that of CA to Cs+ was only 16.4%. Crystal unit cell cubage and parameter a of zeolite and palygorskite adsorbed Cs+ and Sr2+ decreased and change of crystal unit cell parameter a、b and β of zeolite and palygorskite were ruleless.

The role of soil chemistry and soil physics in protecting soil quality: variability of sorption and transport of cadmium as an example.

Soil has many functions in sustaining life. The prerequisite conditions for proper soil functioning may be expessed in terms of quality. Chemical quality of soil is predominantly determined by behaviour of compounds in soil. Compound behaviour is the result of the interactions of properties of the compounds and of the soil system under consideration. These can satisfactorily be described by applying methodical rules as derived in soil chemistry and soil physics. This is elaborated with examples referring to the static situation prevailing at adsorptive equilibrium, and to the dynamic situation of compound displacement in soil. The variability of soil properties appears to be of major concern. In these examples, attention is limited to the behaviour of cadmium in soil. (Abstract retrieved from CAB Abstracts by CABI’s permission)

The modification of apparent thermionic constants for oxygenated tungsten by the temperature variation of adsorptive equilibrium

When the temperature variation of a saturated thermionic current i per unit area is represented by plotting log ( i /T 2 ) against 1/T, it has been customary to identify the slope and the vertical intercept of the graph with the electronic work function ϕ and the logarithm of the emission constant A, respectively, in Richardson’s equation i = AT 2 e - ϕ /k T . This identification has been reasonably successful for materials of a high degree of homogeneity, since they exhibit straight “Richardson plots” whose measurement offers values of A and ϕ not inconsistent with electronic data from other sources. On the other hand, certain materials exhibit curved plots, indicating at once that no fixed A and ϕ can be recorded. Others, with which we are here concerned, give plots which appear straight over an observed range but suggest values of A and ϕ , disagreeing so radically with established theory or with indirect experiments that they have been regarded as anomalous. We prove in one instance that an extension of the range reveals such a plot as part of a curve, and that the curve contains implicit quantities not solely electronic and therefore not expressed by even a sequence of simple Richardson equations. Hence the slopes and intercepts of tangents to this curve are not identifiable with values of ϕ and log A.