In presented work, raw, expanded and acid treated vermiculites were used as low-cost and active adsorbents for reducing of environmental pollution with heavy metals. Acid treatment was performed at elevated temperature (95°C) for 2 and 24 h in solution of HNO3. Adsorption capacity towards Fe3+ was studied in column, semi-batch and batch mode. It was shown that all samples are effective in removal of heavy metals; however adsorption mechanism is based not only on ion exchange of interlayer cations but also precipitation/deposition processes. Starting material and modified samples as well as spent adsorbents were characterized with respect to the vermiculite structure using X-ray diffraction method., Agnieszka Węgrzyn, Lucjan Chmielarz, Paweł Zjeżdżalka, Andrzej Kowalczyk, Magdalena Jabłońska, Xavier Baldrich Tolosa and Marek Michalik., and Obsahuje bibliografii
Kinetic and equilibrium studies of adsorption of arsenates As(V) were investigated in four soils from Slovakia. Using experimentally obtained adsorption isotherms of arsenates, the effect of selected soil properties on its adsorption was studied. The rate of As(V) adsorption was evaluated by three simple kinetic models: Elovich equation, modified Freundlich isotherm and pseudo-second order equation. It can be stated from experimentally obtained and calculated data that an increase in the initial As(V) concentration in solution resulted in a drop in the rate of As(V) adsorption and an increase in the time necessary for an attainment of the adsorption equilibrium. Results from equilibrium studies of As(V) adsorption fitted well to the Freundlich isotherm. The comparison of Freundlich coefficient kF with selected soil properties showed that capacity of particular soil for As(V) retention increased with increasing calcium carbonate content in given soil. The relation between CaCO3 content and kF coefficient was supported by highly positive correlation of dependence kF vs CaCO3, with R2 = 0.868. and Na štúdium rýchlosti adsorpcie arzeničnanov As(V) a ich adsorpčných izoteriem boli použité štyri vzorky pôd. Pomocou experimentálne získaných adsorpčných izoteriem As(V) bol sledovaný aj vplyv niektorých pôdnych vlastností na rozsah adsorpcie As(V). Rýchlosť adsorpcie As(V) bola zhodnotená použitím troch jednoduchých rýchlostných rovníc: Elovichovej rovnice, modifikovanej Freundlichovej izotermy a kinetickej rovnice pseudo-druhého poriadku. Namerané a vypočítané výsledky zo štúdia rýchlosti adsorpcie dokumentujú, že s rastúcou počiatočnou koncentráciou As(V) vo vodnom roztoku sa adsorpčná rýchlosť znížila a čas potrebný na dosiahnutie adsorpčnej rovnováhy sa zvýšil. Experimentálne získané adsorpčné izotermy As(V) veľmi dobre vyhovovali Freundlichovej adsorpčnej izoterme. Zo sledovaných chemických a fyzikálnych vlastností pôd mal na koeficient kF najväčší vplyv obsah uhličitanu vápenatého (CaCO3). Vzťah medzi obsahom CaCO3 a koeficientom kF sa potvrdil vysoko pozitívnou koreláciou (R2 = 0,868).
Adsorption of phenol and aniline onto original and with quaternary ammonium salts (QASs)-modified montmorillonite was described by sorption isotherms of type III and II, respectively. For the montmorillonite (MMT) modification - hydrophobisation, cetyltrimethyl- ammonium (CTMA) and tetramethylammonium (TMA ) cations were used. In comparison with phenol, aniline was adsorbed largely on original MMT but less on modified one. XRD pa tterns indicated that both aromatic compounds were intercalated in the MMT interlayer be ing perpendicularly oriented to silicate sheets. Alkyl chains of CTMA and TMA probably act as organic "pillars" stabilising the MMT tabular structure against exfoliation due to the intercalation with phenol and aniline of high concentrations., Hana Kostelníková, Petr Praus and Martina Turicová., and Obsahuje bibliografické odkazy
Phenolic compounds are common pollutants found particularly in the effluents from petroleum and petrochemical, coal conversion, and phenol producing industries. Due to their toxicity and carcinogenity, water and wastewater containing phenolic compounds must be treated before being used and discharged for receiving water bodies. There is a growing interest in using low-cost and commercially available materials for the adsorption of organic compounds. Clay minerals have great potential to remove phenols in water due to efficient sorbents which can be used as alternative adsorbents to replace the costly activated carbon. They are widely applied in many fields of adsorption technology including the removal of amines, metals, ketones, phosphates, chlorophyll, non-ionic contaminants, and organic pigments/dyes. Montmorillonitic smectites, {(Na,Ca)0.33(Al,Mg)2(Si4O10)-(OH)2.nH2O} are one of the natural clay minerals that have specific surface chemical properties. In this study, a factorial experimental design technique was used to investigate the adsorption of phenol from water solution on montmorillonite. Factorial design of experiments is employed to study the effect of three factors: pH (2.0 and 8.0), montmorillonite dosage (0.1 and 1.0 g/L) and initial low and high concentration (10 and 100 mg/L). The efficiency of phenol adsorption was determined after 60 min of treatment. Main effects and interaction effects of three factors were analyzed by using statistical techniques. A regression model was found to fit the experimental data very well. Through using the Student’s t-test, analysis of variance, F-test and lack of fit to define most important process variables affecting the percentage phenol adsorption., Feza Geyikçi and Semra Çoruh., and Obsahuje bibliografii