1,720,985 research outputs found
The Use of Clay-Polymer Nanocomposites in Wastewater Pretreatment
Get PDFSome agricultural effluents are unsuitable for discharge into standard sewage-treatment plants: their pretreatment is necessary to avoid clogging of the filtering devices by colloidal matter. The colloidal stability of the effluents is mainly due to mutual repulsive forces that keep charged particles in suspension. Pretreatment processes are based on two separate stages: (a) neutralization of the charges (“coagulation”) and (b) bridging between several small particles to form larger aggregates that sink, leaving clarified effluent (“flocculation”). The consequent destabilization of the colloidal suspension lowers total suspended solids (TSSs), turbidity, and other environmental quality parameters, making the treatments that follow more efficient. Clay-based materials have been widely used for effluent pretreatment and pollutant removal. This study presents the use of nanocomposites, comprised of an anchoring particle and a polymer, as “coagoflocculants” for the efficient and rapid reduction of TSS and turbidity in wastewater with a high organic load. The use of such particles combines the advantages of coagulant and flocculant by neutralizing the charge of the suspended particles while bridging between them and anchoring them to a denser particle (the clay mineral), enhancing their precipitation. Very rapid and efficient pretreatment is achieved in one single treatment step
Securing The Future: Clay-Based Solutions For a Comprehensive and Sustainable Potable-Water Supply System
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Addition of a monovalent cationic pesticide to improve efficacy of bipyridyl herbicides in Hulah valley soils
No full textElementary Steps in Steady State Kinetic Model Approximation for the Homo-Heterogeneous Photocatalysis of Carbamazepine
No full textElucidating physicochemical processes in the degradation of pollutants may optimize their removal from water sources. Although the photodegradation of carbamazepine (CBZ) in Advanced Oxidation Processes (AOPs) has been widely studied, there is no detailed report on the elementary steps of the kinetics. This study proposes a set of elementary steps for the AOP of CBZ, combining short-wave ultraviolet radiation (UVC), a homogeneous reagent (H2O2), and a heterogeneous catalyst (TiO2), which includes the excitation of both reagents/catalysts by UVC photons, the adsorption of CBZ by the excited TiO2, or its oxidation by hydroxyl radicals. Assuming the steady-state approximation on the intermediate products (excited TiO2, CBZ-excited TiO2 complex, and hydroxyl radicals) leads to rate laws for the degradation of CBZ, in which UVC radiation, TiO2, and H2O2 are pseudo-first-order at all concentrations or intensities and have no direct influence on CBZ pseudo-order, whereas CBZ shifts from pseudo-first-order at low concentrations to pseudo-zero-order at high concentrations. Several experiments to test the mechanism were conducted by varying CBZ, H2O2, and TiO2 concentrations and UVC radiation intensities. The measured results indeed fit the suggested mechanism for the first three, but the irradiation intensity appears to shift the CBZ influence from pseudo-second- to pseudo-first-order with increased intensities. Part of the elementary steps were changed to fit the results
Eddy correlation measurements to visualize CO2 and water vapor concentrations and fluxes
No full textEddy correlation measures gas exchange between canopy and the overlying atmosphere by evaluating the correlation between fluctuations in the gas-of-interest’s mixing ratio and the vertical wind velocity and considered the most accurate approach for measuring gas fluxes, mostly carbon dioxide and water vapor under ideal homogeneous conditions. It has been used in micrometeorology for decades to quantify mass and energy transfer between urban, natural and agricultural ecosystems and the atmosphere. We assessed its application under various—homogeneous and non-homogeneous—conditions. Our study indicates that fluxes of CO2 and H2O correlate well with plants activity only when turbulent conditions are present, in open fields. At such conditions, direct measurements of concentration of those gases are not an accurate indicator for plants activity. On the other hand, in closed systems (e.g. greenhouses)- fluxes as measured by an eddy correlation system can't accurately be related to the state of the vegetation, but the fluctuations in the concentrations of CO2 and H2O directly correlate to the actual plants activity. Adapting conditions in greenhouses to limiting factors as temperature, increases CO2 sequestration by plants, and may increase productivity
Using a Matlab Implemented Algorithm for UV-vis spectral Resolution for pk<sub>a</sub> Determination and Multicomponent Analysis
No full text A Matlab implemented computer code for spectral resolution is presented. The code enables the user to resolve the UV-visible absorption spectrum of a mixture of up to 3 previously known components, to the individual components, thus, evaluating their quantities. The resolving procedure is based on searching the combination of the components which yields the spectrum which is the most similar (minimal RMSE) to the measured spectrum of the mixture. Examples of using the software for pKa value estimation and multicomponent analysis are presented and other implementations are suggested. </jats:p
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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