Equilibrium, kinetic and thermodynamic studies on the removal of U(VI) by low cost agricultural waste

In this research, biosorption efficiency of different agro-wastes were evaluated with rice husk showing maximum biosorption capacity among the selected biosorbents. Optimization of native, SDS-treated and immobilized rice husk adsorption parameters including pH, biosorbent amount, contact time, initial U(VI) concentration and temperature for maximum U(VI) removal was investigated. Maximum biosorption capacity for native (29.56 mg g-1) and immobilized biomass (17.59 mg g-1) was observed at pH 4 while SDS-treated biomass showed maximum removal (28.08 mg g-1) at pH 5. The Langmuir sorption isotherm model correlated best with the U(IV) biosorption equilibrium data for the 10-100 mg L-1 concentration range. The kinetics of the reaction followed pseudo-second order kinetic model. Thermodynamic parameters like free energy (ΔG°) and enthalpy (ΔH°) confirmed the spontaneous and exothermic nature of the process. Experiments to determine the regeneration capacity of the selected biosorbents and the effect of competing metal ions on biosorption capacity were also conducted. The biomass was characterised using scanning electron microscopy, surface area analysis, Fourier transformed infra-red spectroscopy and thermal gravimetric analysis. The study proved that rice husk has potential to treat uranium in wastewater

Porous structure of natural and modified clinoptilolites

Abstract The evaluation of the pore-size distribution (PSD) of natural and modified mesoporous zeolites, i.e., clinoptilolites is presented. We demonstrate the SEM results showing that the pores of fracture-type from 25-50 nm to 100 nm in size between clinoptilolite grains, as well as pores between crystal aggregates up to 500 nm in size are present in the studied material. The detailed distribution of pore sizes and tortuosity factor of the above-mentioned materials are determined from the adsorption-desorption isotherms of nitrogen measured volumetrically at 77 K. To obtain the reliable pore size distribution (PSD) of the above-mentioned materials both adsorption and desorption branches of the experimental hysteresis loop are described simultaneously by recently developed corrugated pore structure model (CPSM) of Androutsopoulos and Salmas. Evaluated pore size distributions are characterized by well-defined smooth peaks placed in the region of the mesoporosity. Moreover, the mean pore diameter calculated from the classical static measurement of nitrogen adsorption at 77 K correspond very well to the pore diameters from SEM, showing the applicability of the CPSM for characterization of the porosity of natural zeolites. We conclude that classical static adsorption measurements combined with the proper modeling of the capillary condensation/evaporation phenomena are a powerful method which can be applied for pore structure characterization of natural and modified clinoptilolites

Adsorptive removal of ciprofloxacin and isoniazid from aqueous solution

This paper describes study of ciprofloxacin and isoniazid removal from aqueous solutions using coal fly ash (FA), kaolinite, perlite, talc and vermiculite. The adsorptive features of the adsorbents were evaluated for ciprofloxacin and isoniazid with regards to the effects of contact time, pH, the solid/liquid ratio and antibiotic concentration. All adsorbents were sterilised by dry heat before use to avoid the proliferation of antimicrobial resistance by the bacteria present on the adsorbents during experiments. The regression correlation coefficients indicate that the Langmuir model gives the best fit for the sorption of both antibiotics onto FA and talc, ciprofloxacin onto kaolinite, and isoniazid onto perlite and vermiculite with R2 values ranging from 0.908 – 0.999. The Freundlich isotherm best describes the sorption of ciprofloxacin onto vermiculite and isoniazid onto kaolinite with R2 values of 0.999 for both. The Tempkin model best describes the sorption of ciprofloxacin onto perlite with an R2 = 0.997. The values of the Freundlich exponent, 1/n, range from 0.221 – 0.998, indicating a favourable adsorption of ciprofloxacin and isoniazid onto the adsorbents. The heat of sorption, B, calculated from the Temkin plots has values ranging from 0.018 – 10.460 J/mol, indicating a physical adsorption process (physisorption). Adsorption equilibrium was achieved after 30 min for both antibiotics and the kinetic data obtained conforms best to the pseudo-second order equation with R2 values ranging from 0.998 – 0.999. The removal of ciprofloxacin and isoniazid by all adsorbents except FA was strongly influenced by the pH suggesting that electrostatic interactions play a major role in the adsorption processes

Removal of Lead from aqueous phase using Amberlite and natural Zeolite

Two following reason lead (Pb) us to find a way for removing heavy metals (HM) from the water resources, first limitation of water resource and increasing of water scarcity and second increaseing of surface and groundwater contamination by HM, (derived from industrial and municipal wastewater). In this research, Zeolite (Clinoptilolit) as natural and Amberlite (IR-120) as chemical were used as sorbents of Pb. Experiments were done in batch mode under various operational conditions including three size of zeolite and one mean diameter of Amberlite. An splite-plot experimental design was employed with 60 treatments and three replications at Shiraz University, Shiraz, Iran in 2011. The treatment were five different concentration of the Pb contamination and three size of zeolite (0.075, 0.2 and 0.42mm). The concentration for Pb were: 40, 250, 500, 1000. The removing efficiency of the zeolite and Amberlite was measured for Pb. The results showed that the effect of concentration of contamination and zeolite size were statisticaly significant. It showed that by increasing of the concentration of contamination, absorption of the HM increases linearly by zeolite. Maximum Pb absorption occurred at 1250 mg/l with a value of 59.97 mg for 1 grams of zeolite. The minimum Pb absorption occurred at 40 mg/l with a value of 1.82 mg for 1 grams of zeolite. The results showed that the effect of concentration of HM were statisticaly significant for Amberlite and it also observed that the absorption of HM by Amberlite increases linearly. Maximum Pb absorption occurred at 1250 mg/l with a value of 62.35 mg for 1 grams of Amberlite. The minimum Pb absorption occurred at 40 mg/l with a value of 1.98 mg for 1 grams of zeolite

Catalytic Isomerization of Dihydroxyacetone to Lactic Acid and Alkyl Lactates over Hierarchical Zeolites Containing Tin

Hierarchical zeolites containing tin were obtained, characterized and used in a reaction of catalytic isomerization of dihydroxyacetone (DHA) to lactic acid and alkyl lactates. These catalysts are characterized by preserved crystallinity and primary microporosity with the simultaneous existence of secondary porosity regarding mesopores, which facilitates access of large molecules of reagents to active centers. Creation of additional porosity was confirmed by X-ray diffraction and low-temperature nitrogen adsorption/desorption studies. The reaction of dihydroxyacetone isomerization was conducted in different reaction media such as methanol, ethanol or water with the use of two heating methods: microwave radiation and conventional heating. The application of microwave radiation enabled to reduce the reaction time to 1 h and achieve dihydroxyacetone conversion of >90% and high yields of the desired reaction products

Studies on selected properties of natural mineral modified leathers with the addition of polyhexamethylenebiguanide-based preparation

Zbadano strukturę i wybrane parametry fizyko-mechaniczne, higieniczne i mikrobiologiczne podszewkowych skór obuwiowych z wypełnieniem opartym na naturalnych kompozytach mineralnych: zeolicie (MMZ), montmorylonicie (MMT) z dodatkiem preparatu na bazie poliheksametylenobiguanidy (PHMB). Badania wykazały poprawę badanych właściwości modyfikowanych próbek w odniesieniu do skór bez dodatku PHMB.The structure and the selected physical and mechanical, hygienic and microbiological parameters of footwear lining leather with filling based on natural mineral composite materials: zeolite (MMZ), montmorillonite (MMT) with an addition of a preparation based on polyhexamethylene biguanide (PHMB) were tested. The research has shown an improvement in the tested properties of the modified samples in relation to leather without PHMB

The Study of Zinc Ions Binding to αS1-, β- and κ-Casein

The presented studies focused on the specificity binding of particular casein fractions: αS1-, β- and κ-casein (αS1CN, βCN, κCN), with zinc ions. The binding mechanism was determined by kinetic modeling using results of batch sorption. For this goal, models of zero-order kinetics, pseudo-first-order, pseudo-second-order and Weber–Morris intraparticle diffusion were used. The formation of Zn-αS1CN, Zn-βCN and Zn-κCN complexes was additionally monitored using spectroscopic methods such as Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopy, characterizing active functional groups involved in the binding process. Additionally, a mass spectrometry technique—matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS)—was used to characterize respective protein fractions and obtained complexes. Spectroscopic and spectrometric studies were carried out both before and after binding the protein with zinc ions. The obtained results showed the difference in Zn-αS1CN, Zn-βCN and Zn-κCN complexes created at separate kinetic stages. On the basis of instrumental studies, a significant influence of acidic (glutamic acid (Glu), aspartic acid (Asp)) and aromatic (tryptophan (Trp), phenylalanine (Phe), tyrosine (Tyr)) amino acids on the formation of metal complexes was proven. In turn, spectrometric studies allowed determining the molecular masses of casein isoforms before and after binding to zinc ions