Kinetics of adsorption and hydrodynamic cavitation removal of phenol from wastewater

На основу добијених резултата утврђено је да зеолит типа силикалит селективно адсорбује фенол из водених раствора и да је адсорпција фенола на силикалиту спонтани, егзотермни, термички активирани процес. Брзина адсорпције фенола на силикалиту је кинетички ограничена брзином раста адсорпционог слоја. Кинетика адсорпције фенола може се описати моделом - реакција контролисана брзином померањa површине граничне фазе. Утврђено је да је енергија активације за адсорпцију фенола независна од степена адсорпције фенола. Предложен је нови модел за кинетику адсорпције полутаната из њихових водених раствора на зеолитима који се успешно примењује за темељно објашњење испитиване адсорпције фенола на зеолиту типа силикалит. Конструисан је кавитатор типа плоча са отворима и кавитатор Вентуријевог типа. Одређене су вредности оптималних реакционих параметара кавитационог уклањања фенола из отпадних вода укључујући температуру, концентрацију водоник пероксида, вредности кавитационог броја и pH вредност. Утврђено је да технологија хидродинамичке кавитације без додатних хемикалија омогућава да се постигне ограничени степен уклањања фенола. Повећање температуре и концентрације водоник пероксида, као и смањење вредности кавитационог броја и pH вредности раствора доводи до повећања степена уклањања фенола. Потпуно уклањање фенола из раствора се постиже у веома кратком временском интервалу за одређени стехиометријски однос водоник пероксида и фенола у реакционом раствору. Кинетика уклањања фенола у условима хидродинамичке кавитације са кавитатором оба типа може се описати кинетичким моделом хемијске реакције првог реда у односу на водоник пероксид.Based on the obtained results it was found that zeolite type silicalite adsorbs phenol from aqueous solutions selectively and that adsorption of phenol on silicalite is a spontaneous, exothermic, thermally activated process. The rate of adsorption of phenol on silicalite is kinetically limited with the increase in the rate of adsorption layer. The kinetics of phenol adsorption can be described by the model, known as - a reaction controlled by the rate of movement of the area of boundary phase. It was found that the activation energy for phenol adsorption is independent on the degree of phenol adsorption. A new model has been proposed for the kinetics of adsorption of pollutants from their aqueous solutions on zeolites, which has been successfully applied to thoroughly explain the investigated adsorption of phenols on zeolite type silicalite. A novel model for the kinetics of adsorption of pollutants from their aqueous solutions on zeolites was proposed, which is successfully applied to give comprehensive explanation of the investigated adsorption of phenol on zeolite type silicalite. Both cavitators orifice plates and Ventury type cavitator were constructed. The values of the optimal reaction parameters for phenol removal by using cavitation from waste water that include temperature, hydrogen peroxide concentration, cavitation number and pH, were determined. It has been found that hydrodynamic cavitation technology without additional use of chemicals enables to achieve a limited degree of phenol reduction. The increase in temperature and in the concentration of hydrogen peroxide, as well as the decrease in the value of the cavitation number and the pH values of the solution, leads to the increase in the in the degree of phenol removal. The complete reduction of phenol from solution is achieved in a very short time interval for the certain stoichiometric ratio of hydrogen peroxide to phenol in the reaction solution. The kinetics of phenol removal under the conditions of hydrodynamic cavitation using both types of cavitators can be described with a first-order kinetic chemical model calculated against the concentration of hydrogen peroxide..

Dinuclear silver(I) complexes with a pyridine-based macrocyclic type of ligand as antimicrobial agents against clinically relevant species: the influence of the counteranion on the structure diversification of the complexes

New dinuclear silver(i) complexes withN,N ',N '',N '''-tetrakis(2-pyridylmethyl)-1,4,8,11-tetraazacyclotetradecane (tpmc), [Ag-2(NO3)(tpmc)]NO3 center dot 1.7H(2)O (1), [Ag-2(CF3SO3)(2)(tpmc)] (2), and [Ag-2(tpmc)](BF4)(2) (3) were synthesized and characterized by NMR (H-1 and(13)C), IR and UV- Vis spectroscopy, cyclic voltammetry and molar conductivity measurements. The molecular structures of the complexes were determined by single-crystal X-ray diffraction analysis. The spectroscopic and crystallographic data showed that the structure of the complexes strongly depends on the nature of the counteranion of silver(i) salt used for their synthesis. The antimicrobial activity of complexes1-3was examined against Gram-positive and Gram-negative bacteria and different species of unicellular fungus Candida spp. The ability of these complexes to inhibit the formation of Candida biofilms and to eradicate the already formed biofilms was tested in the standard microtiter plate-based assay. In addition, a bioelectrochemical testing of the antimicrobial activity of complex 1 against early biofilm was also performed. The obtained results indicated that complexes 1-3 showed increased activity toward Gram-negative bacteria and Candida spp. and could inhibit the formation of biofilms. In most cases, these complexes had positive selectivity indices and showed similar or even better activity with respect to the clinically used silver(i) sulfadiazine (AgSD). The values of the binding constants for complexes 1-3 to bovine serum albumin (BSA) were found to be high enough to indicate their binding to this biomolecule, but not so high as to prevent their release upon arrival at the target site. Moreover, the positive values of partition coefficients for these complexes indicated their ability to be transported through the cell membrane. Once inside the cell, complexes 1-3 could induce the formation of the reactive oxygen species (ROS) in C. albicanscells and/or interact with DNA. Taken together, silver(i) complexes with the tpmc ligand could be considered as novel antimicrobial compounds with favourable pharmacological properties, being safer than AgSD