Uklanjanje arsena iz vode adsorpcijom na nekonvencionalnim materijalima

This paper deals with arsenic removal from water by adsorption with unconventional materials: natural materials (zeolite, bentonite, sepiolite, limonite, pyrolusite), waste materials (waste iron slag, waste sand filter) and modified materials (neutralized waste iron slag, iron(III)-hydroxide coated sand and activated carbon). Under the same conditions are investigated commercial sorbents to compare results. Arsenic removal by adsorption with unconventional materials is investigated in the batch reactor. The best results in batch reactor are obtained with waste materials. Waste iron slag and waste filter sand exhibited equilibrium sorption capacities of 50 μg/g and 30 μg/g, respectively, which is nearly equal to values obtained for the commercial sorbents. Due to the high content of CaO waste iron slag increases significantly water pH (pH=11). In order to minimize its deteriorating impact on the initial water quality, the waste iron slag was neutralized. The new, modified waste iron slag exhibited the highest sorption capacity, 55.U ovom radu su prikazani rezultati istraživanja efikasnosti uklanjanja arsena iz vode sorpcijom na nekonvencionalnim materijalima: prirodnim (zeolit, bentonit, sepiolit, limonit, piroluzit), otpadnim (otpadna šljaka, otpadni filtarski pesak) i modifikovanim (modifikovana otpadna šljaka, kvarcni pesak i aktivni ugalj impregnisani gvožđe(III)-hidroksidom). Pod istim uslovima paralelno su ispitivani komercijalni sorbenti radi poređenja rezultata. Uklanjanje arsena iz vode sorpcijom je ispitivana u šaržnom sistemu Najbolji rezultati u šaržnom sistemu dobijeni su sa otpadnim materijalima: za otpadnu šljaku i 30 μg/g za otpadni filtarski pesak (za Co=0,5 mg/L), što je u nivou vrednosti koje su dobijene za komercijalne sorbente za uklanjanje arsena. Zbog visokog sadržaja CaO, otpadna šljaka značajno povećava pH vrednost vode (pH= 11). Neutralizacijom otpadne šljake dobijen je nov materijal, modifikovana otpadna šljaka, većeg sorpcionog kapaciteta: 55

A New Approach in Regression Analysis for Modeling Adsorption Isotherms

Numerous regression approaches to isotherm parameters estimation appear in the literature. The real insight into the proper modeling pattern can be achieved only by testing methods on a very big number of cases. Experimentally, it cannot be done in a reasonable time, so the Monte Carlo simulation method was applied. The objective of this paper is to introduce and compare numerical approaches that involve different levels of knowledge about the noise structure of the analytical method used for initial and equilibrium concentration determination. Six levels of homoscedastic noise and five types of heteroscedastic noise precision models were considered. Performance of the methods was statistically evaluated based on median percentage error and mean absolute relative error in parameter estimates. The present study showed a clear distinction between two cases. When equilibrium experiments are performed only once, for the homoscedastic case, the winning error function is ordinary least squares, while for the case of heteroscedastic noise the use of orthogonal distance regression or Margart's percent standard deviation is suggested. It was found that in case when experiments are repeated three times the simple method of weighted least squares performed as well as more complicated orthogonal distance regression method

Formation of complex two-dimensional dissipative solitons via spontaneous symmetry breaking

We propose a complex Ginzburg-Landau equation (CGLE) with localized linear gain as a two-dimensional model for pattern formation proceeding via spontaneous breaking of the axial symmetry. Starting from steady-state solutions produced by an extended variational approximation, simulations of the CGLE generate a vast class of robust solitary structures. These are varieties of asymmetric rotating vortices carrying the topological charge (TC), and four- to ten-pointed revolving stars, whose angular momentum is decoupled from the TC. The four- and five-pointed stars feature a cyclic change of their structure in the course of the rotation