Influence of the support base on the sorption of Co(II) with mixed solvents

Theonyltrifluoroacetone (TTA) mixed with trioctyl phosphine oxide (TOPO) have been supported on Amberlite XAD-4, silica gel and wood powder. The resulting resins have been used to study the sorption of cobalt(II) from acetate buffer and their sorption capacities were determined and were found to be 12.38, 11.61 and 6.51 mg g(-1) for TTA+TOPO/Amberlite XAD4, TTA+TOPO/silica gel and TTA+TOPO/wood, respectively. The experimental results showed that the sorption of Co(II) increases with its initial concentration. The results can be fitted by Freundlich isotherm in the studied cobalt concentration range [10(-4)-10(-3) M] and 1/n values are 1.07, 1.17 and 1.73 for Amberlite XAD4, silica gel and wood powder, respectively. The sorption of Co(II) onto the prepared resins was found to follow the pseudo-second order model and the sorption rate have the values 8.79x10(-3), 10x10(-3) and 16x10(-3) g mg(-1)min(-1) for Amberlite XAD4, silica gel and wood powder, respectively. Thermodynamic parameters have also been calculated for the three systems and sorption process was found to be spontaneous and endothermic one.     

Experimental study of the refrigeration cycle performance for the R744/R290 mixtures

A new binary mixture of R744 and R290 as an alternative natural refrigerant to R13 was first presented in this paper. Its environmental performance is friendly. It has an ODP of zero and GWP smaller than 20. Experimental studies for this mixture and R13 were performed on a cascade refrigeration system only with modification to capillary in low-temperature circuit. COP and refrigeration capacity of this binary mixture were higher than those of R13, at the same time, condensing pressure, evaporating pressure, compression ratio, and discharge temperature were also higher than that of R13 when the high-temperature circuit of cascade refrigeration system was kept invariable. The new binary mixture of R744 and R290 is considered as a promising alternative refrigerant to R13 when the evaporator temperature is higher than 201 K.     

Sorption profile of Cd(II) ions onto beach sand from aqueous solutions

Sorption of traces of Cd(II) ions onto beach sand is investigated as a function of nature and concentration of electrolyte (10(-4) to 10(-2)M nitric, hydrochloric and perchloric acids, pH 2-10 buffers and deionized water), shaking time 5-40min, shaking speed 50-200strokes/min, dosage of sand (50-1000mg/15cm(3)), concentration of sorbate (1.04x10(-6) to 1.9x10(-4)M) and temperature (293-323K). Maximum sorption of Cd(II) ions (approximately 66%) is achieved from deionized water using 300mg/15cm(3) sand in 20min. The data are successfully tested by Langmuir, Freundlich and Dubinin-Redushkevich (D-R) sorption isotherms. The values for characteristic Langmuir constants Q=13.31+/-0.20micromol/g and of b=(6.56+/-0.53)x10(3)dm(3)/mol, Freundlich constants A=2.23+/-1.16mmol/g and 1/n=0.70+/-0.05 of (D-R) constants beta=-0.005068+/-0.000328kJ(2)/mol(2), X(m)=46.91+/-11.91micromol/g and energy E=9.92+/-0.32kJ/mol have been estimated. Kinetics of sorption has been studied by applying Morris-Weber, Richenberg and Lagergren equations. The sorption follows first order rate equation resulting 0.182+/-0.004min(-1) The thermodynamic parameters DeltaH=32.09+/-2.92kJ/mol, DeltaS=111.0+/-9.5J/molK and DeltaG=-1.68+/-0.02kJ/mol are evaluated. The influence of common ions on the sorption of Cd(II) ions is also examined. Some common ions reduce the sorption while most of the ions have very little effect. It can be concluded that beach sand may be used as an alternative for the expensive synthetic sorbents.     

Removal of copper(II) from aqueous solution by Jordanian pottery materials

The aim of this work was to assess the possibility of removing some heavy metals from water by a low-cost adsorbent, like Jordanian raw pottery. Five types of raw and modified pottery materials have been investigated. The effects of initial metal concentration, agitation time, pH and temperature on the removal of Cu(II) were studied. A pseudo-first order was used to test the adsorption kinetics. In order to investigate the sorption isotherm, two equilibrium models, the Freundlich and Langmuir isotherms, were analyzed. The effect of solution pH on the adsorption onto pottery was studied in the pH range 1-5. The adsorption was exothermic at ambient temperature and the computation of the parameters, DeltaH, DeltaS and DeltaG, indicated the interactions to be thermodynamically favorable.     

Metal sorption on soils as affected by the dissolved organic matter in sewage sludge and the relative calculation of sewage sludge application

To evaluate the influences of sewage sludge-derived organic matters on metal sorption and on the resultant sludge loading estimates, a batch experiment was conducted to compare the sorption of Ni, Cu and Pb in sewage sludge filtrates (1:20 sewage sludge to water) on eight soils and the adsorption of metals in a reference solution which had the same matrix as the sewage sludge filtrate except dissolved organic material (henceforth referred to as reference solution). Metal sorption could be well fitted by linear isotherm and the dissolved organic matter in sludge significantly depressed the sorption (p<0.01). The main factor controlling sorption of Ni on different soils was dominated by soil cation exchange capacity (CEC) and sorption of Cu and Pb was by soil organic matter (SOM). The parameters obtained from the sorption isotherm equations were then used to estimate sludge loadings into the soils. When the sorption parameters derived from the reference solution were used for calculation, that is the effect of dissolved organic matter was not considered, the calculated safe application rates are approximately 47.8, 51.4, 34.2, 31.3, 21.7, 46.3, 187.1 and 27.6 t-sludge/ha for the Beijing, Jiangxi, Xiamen, Jilin, Guangdong, Wuhan, Gansu and Xinjiang soils, respectively. However, when the sorption parameters derived from the dissolved organo-metallic complexes are used for calculation, the corresponding application rates are reduced to approximately 6.0, 3.4, 1.9, 10.0, 6.3, 3.6, 7.3 and 3.5 t-sludge/ha, respectively. By this study we can get a conclusion that the effect of sewage sludge derived dissolved organic matter on heavy metal sorption and soil properties should be considered in the course of regulating the safe application rates of sewage sludge to soil.     

Batch sorption dynamics and equilibrium for the removal of cadmium ions from aqueous phase using wheat bran

Studies on a batch sorption process using wheat bran as a low cost sorbent was investigated to remove cadmium ions from aqueous solution. The influence of operational conditions such as contact time, cadmium initial concentration, sorbent mass, temperature, solution initial pH, agitation speed and ionic strength on the sorption kinetics of cadmium was studied. Pseudo-second-order model was evaluated using the six linear forms as well as the non-linear curve fitting analysis method. Modeling of kinetic results shows that sorption process is best described by the pseudo-second-order model using the non-linear method. The sorption of cadmium was found to be dependent on initial concentration, sorbent mass, solution pH, agitation speed, temperature, ionic strength and contact time. The value of activation energy (12.38 kJ mol(-1)) indicates that sorption has a low potential barrier corresponding to a physical process. Sorption equilibrium isotherms at different temperatures was determined and correlated with common isotherm equations such as Langmuir and Freundlich models. It was found that the Langmuir model appears to well fit the isotherm data but a worse correlation was obtained by the Freundlich model. The five Langmuir linear equations as well as the non-linear curve fitting analysis method were discussed. Results show that the non-linear method may be a better way to obtain the Langmuir parameters. Thermodynamic parameters such as DeltaH degrees, DeltaS degrees and DeltaG degrees were calculated. These parameters indicate that the sorption of cadmium by wheat bran is a spontaneous process and physical in nature involving weak forces of attraction and is also endothermic.     

Removal of copper and nickel ions from aqueous solutions by grape stalks wastes

In the present work, the usefulness of grape stalks wastes generated in the wine production process has been investigated for the removal of copper and nickel ions from aqueous solutions. The sorption process was relatively fast and equilibrium was reached after about 60 min of contact. The influence of pH, sodium chloride and metal concentration on metal removal has been studied. Uptake showed a pH-dependent profile. Maximum sorption for both metals was found to occur at around pH 5.5-6.0. An increase of sodium chloride concentration caused a decrease in metal removal. Langmuir isotherms, at pH 6.0, for each metal were used to describe sorption equilibrium data. Maximum uptake obtained was 1.59x10(-4) mol of copper and 1.81x10(-4) mol of nickel per gram of dry sorbent. Sorption of copper and nickel on grape stalks released an equivalent amount of alkaline and alkaline earth metals (K+, Mg2+, Ca2+) and protons, indicating that ionic exchange is predominantly responsible for metal ion uptake. Fourier transform infrared (FTIR) spectrometry analysis indicated that lignin C-O bond might be involved in metal uptake. Equilibrium batch sorption studies were also performed using a two metal system containing (Cu(II)+Ni(II)). In the evaluation of the two metal sorption system performance, single isotherm curves had to be replaced by three-dimensional sorption isotherm surface. In order to describe the isotherm surface mathematically, the extended-Langmuir model was used. Nickel was found to be much more sensitive to the presence of copper than copper is to the presence of nickel.     

A rapid method to measure the solid-water distribution coefficient (Kd) for pharmaceuticals and musk fragrances in sewage sludge

Pharmaceuticals and personal care products are omnipresent in wastewater world-wide. In order to predict their sorption quantities onto sludge in wastewater treatment plants (WWTPs), the solid-water distribution coefficients (Kd values) of selected pharmaceuticals (antiphlogistics, estrogens, lipid regulators, anti-epileptic and cytostatic agents) and polycyclic musk fragrances (HHCB, AHTN) were determined in primary and secondary sludges taken from a German municipal WWTP. For the Kd determination, batches of primary and secondary sludge slurries were spiked with the respective target compounds and slowly stirred under defined conditions (e.g. an argon atmosphere). Finally, the water and solid sludge phases were analysed. The Kd values of pharmaceuticals ranged from <1 to 500 L kg(-1), while those for the polycyclic musk fragrances AHTN and HHCB proved to be up to 5300 and 4900 L kg(-1), respectively. The primary and secondary sludge showed significant differences for some pharmaceuticals such as Diclofenac and Cyclophosphamide due to the different pH and composition of the two sludges. The removal rate from the water phase caused by sorption in a WWTP can be reasonably predicted on the basis of the Kd values.     

The effect of temperature on toluene sorption by granular activated carbon and its use in permeable reactive barriers in cold regions

Granular activated carbon (GAC) has been used as an adsorbent for hydrocarbons in a range of permeable reactive barriers. This work investigates the influence of temperature on adsorption performance. In particular, the influence of temperature in the range of 20 °C to 4 °C on the sorption equilibrium and kinetics of toluene on GAC surface were investigated. The results show that low temperature leads to decreased toluene sorption by GAC and slower reaction kinetics. Sorption kinetics studies show that diffusion coefficients are also lower at 4 °C (3.65 × 10⁻¹³ m² s⁻¹) than 20 °C (5.112 × 10⁻¹³ m² s⁻¹).     

Phenanthrene sorption to Chinese coal: importance of coal's geochemical properties

Phenanthrene (Phen) was chosen as the probe compound for determining the sorption of PAHs to a series of different coal samples from China. Based on elemental analysis and nuclear magnetic resonance (NMR) spectra analysis, coal samples were characterized with different metamorphic evolutional degrees. The experimental sorption data were fitted well by the Freundlich model, suggesting enhanced sorption capacity and strong nonlinearity of coal samples. The combined partition and adsorption model yielded a better fit than the Freundlich isotherm, indicating that adsorption dominated the sorption at low aqueous concentrations. Correlations between coal properties and sorption capacity values indicated that C%, H/C and O/C atomic ratios were the key factors controlling the sorption behavior. Compared to total carbon, BC might play more important role in the sorption of Phen to coal samples. Moreover, there existed nonlinear relationships between combined carbon, aromatic and aliphatic carbon contents and log K_Fr and n values, respectively, indicating the significance of aromatic and aliphatic carbon in the coal sorption behavior.