Brewers' spent grain (BSG), a lignocellulosic waste material, was evaluated as a low-cost adsorbent for the removal of synthetic dyes methylene blue (MB) and Congo red (CR) from aqueous solutions in a batch process. Characterisation of the BSG was performed by chemical analysis, FTIR and SEM. The effects of contact time, initial dye concentration, adsorbent particle size, adsorbent concentration and pH on the adsorption process were investigated. High removal of both dyes ranging from 70 to over 90 % was achieved. It was shown that in both cases (MB and CR adsorption) the process could be interpreted in terms of Langmuir and Freundlich adsorption isotherms. The kinetics of the adsorption process was well described by the pseudo-second-order model. The results indicated the potential use of BSG as a low-cost adsorbent for MB and CR dye removal from aqueous solutions.
No abstract
The growth kinetics and properties of potentiodynamically formed thin oxide films on Al were investigated in 0.05 M citric acid solutions of different pH (5, 6 and 7) by means of potentiodynamic polarization and a.c. electrochemical impedance spectroscopy (EIS) measurements. Al showed passive behaviour within the pH range that was examined. The potentiodynamic growth of the oxide film on Al takes place due to ionic conductivity under the influence of the high electric field. Characteristic kinetic oxide film growth parameters such as the high-field growth exponential law constants (A and B), ionic conductivity through the oxide film, field strength and half barrier width have been calculated. Impedance measurements were used to determine the parameters related to the characteristic sizes and properties of oxide film. The capacitive response of the impedance spectrum was related to the thickness and dielectric properties of the barrier oxide film. The oxide film resistance values were very high, indicating that the oxide films formed under potentiodynamic conditions are highly uniform in thickness and very resistant. The anodic behaviour of Al in the citric solutions under potentiodynamic conditions were characterized by the rapid growth of the oxide film which diminished the influence of relaxation processes on the growth kinetics and structural characteristics of the aluminium/anodic oxide film/electrolyte system.
Purpose -This paper aims to explore a theoretical and methodological approach to preservation management in libraries, relying on the basic presumption that preservation is a complex and comprehensive process that involves many different and seemingly diverse aspects whose efficiency lies in preservation management. Design/methodology approach -Using a case study of Croatia, the paper describes a methodology for exploring the general preservation management context and presents a preservation management model that comprises five key components. Findings -The paper offers insight into preservation management issues in a specific national context. Research limitations/implications -Although this paper focuses primarily on written heritage in libraries, it is applicable to other types of heritage and to other types of information institutions. Practical implications -The theoretical and methodological approach presented in this paper and described in the example of Croatia can be useful for exploring similar issues in other countries. It can be expanded to other types and forms of heritage and heritage institutions. Originality/value -The paper describes a model of organising preservation activities into an efficient and successful preservation system, and establishes a methodology for exploring diverse preservation issues on national and institutional levels.
Selenium levels in human milk in the winter period ranged from 5.3 micrograms/l to 23.8 micrograms/l, the mean value being 11.0 micrograms/l. The nursing women were divided into several groups according to the results of a questionnaire, i.e. according to their social status (refugees or otherwise), number of deliveries, post partum days, the weight they had gained during pregnancy, their age and smoking habits. The mean levels of selenium for each group are presented. Selenium was determined by hydride generation atomic absorption spectrometry.
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