Uranium(VI) adsorption on graphene oxide nanosheets from aqueous solutions

This paper presents a brief overview of improved Liquid membrane (LM) separation techniques. including modified bulk, supported and emulsion liquid membranes as well as hollow fibre contained liquid membranes, electrostatic pseudo liquid membranes (ESPLIM) reverse micelle and recently developed hybrid (HLM) and other LM configurations. The discussion also includes design of ion specific carriers, analytical importance, aspects of stability and modelling of LMs and their applications in the separation/removal of metal captions from a range of diverse matrices. In general, an attempt has been made to review the literature published from 1990 to 1997 in order to focus on the present status of different liquid membrane configurations. The LM studies dealing with separation and removal of organic compounds and gases are not included in this article owing to limitations of space.

Improved Techniques in Liquid Membrane Separations: An Overview

The present work deals with the use of multiple-step procedures to obtain valuable sub-products, including nanocellulose, from rice husk. Each sub-product was characterized after every step by analyzing the chemical composition (mainly based on thermogravimetric analysis, Fourier transformed infrared spectra, and X-ray diffraction) and morphology (using visual observations and scanning electron microscopy). The results clearly showed that the selected procedure gave the possibility to separate silica in the first step and then to purify the resultant material, leading to nanocellulose production. All acquired sub-products can be used as additives and fillers in a very wide range of applications. The obtained results will be useful both from technological and academic points of view, mainly for people working in the field of biocomposites. The final material could give added value to a raw biomass material source such as rice husk.

https://ojs.cnr.ncsu.edu/index.php/BioRes/article/download/BioRes_06_2_1440_Luduena_FAS_Nanocellulose_Rice_Husk/934

Nanocellulose from rice husk following alkaline treatment to remove silica

Recent development in derivative ultraviolet/visible absorption spectrophotometry: 2004-2008: a review.

Ionophore incorporated PVC membrane sensors are well-established analyticaltools routinely used for the selective and direct measurement of a wide variety of differentions in complex biological and environmental samples. Potentiometric sensors have someoutstanding advantages including simple design and operation, wide linear dynamic range,relatively fast response and rational selectivity. The vital component of such plasticizedPVC members is the ionophore involved, defining the selectivity of the electrodes' complexformation. Molecular recognition causes the formation of many different supramolecules.Different types of supramolecules, like calixarenes, cyclodextrins and podands, have beenused as a sensing material in the construction of ion selective sensors. Schiff's bases andcrown ethers, which feature prominently in supramolecular chemistry, can be used assensing materials in the construction of potentiometric ion selective electrodes. Up to now,more than 200 potentiometric membrane sensors for cations and anions based on Schiff's bases and crown ethers have been reported. In this review cation binding and anioncomplexes will be described. Liquid membrane sensors based on Schiff's bases and crownethers will then be discussed.

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Schiff's Bases and Crown Ethers as Supramolecular Sensing Materials in the Construction of Potentiometric Membrane Sensors

A new method has been developed to reduce the concentration of Ferric ions present as inorganic impurities in crude Egyptian phosphoric acid. This method is based on the silica extracted by alkaline treatment of rice husk to carry out the exchange of ions. Several parameters (contact time, temperature, sorbent type, sorbent mass, and batch factor) were examined. Simultaneous determination of Fe 3+ ions in presence of uranium ions before and after treatment revealed that the concentration of uranium was reduced by ∼18% during the removal of Fe 3+ . Adsorption isotherm indicates that the monolayer coverage is 0.386 g Fe 3+ ions per g sorbent. In dynamic mode, the adsorption capacity at ( C e / C o =50% or Q 0.5 ) was=22.5 mg/g and the column recycled at least three times and only needs 150 ml of 0.1 M HNO 3 for each regeneration and no weight loss in sorbent per cycle should be considered. Therefore, the developed rice husk adsorbent is considered as a better replacement technology for removal of Fe 3+ ions due to its low cost and good efficiency in this application. The cost of 1 kg of the modified rice husk (MRH) is estimated and the sorption mechanism is discussed.

Purification of wet phosphoric acid from ferric ions using modified rice husk

The extraction of uranyl ions from different phosphoric acid media by CYANEX-921 (a commercial trioctyl phosphine oxide) mixed with di-2-ethylhexyl phosphoric acid diluted with odourless kerosene has been investigated. The effect of phosphoric acid, CYANEX-921 and HDEHP concentrations, as well as temperature on the extraction were studied. The extraction rate for UO22+ transfer from 5 M phosphoric acid to the organic phase containing a CYANEX-921–HDEHP mixture in a single drop column without external force was also studied. The mass transfer of uranium in the organic extractant single drop was investigated in terms of drop size, uranium concentration as well as other parameters. The extraction rate was found to be mainly dependent on uranium, HDEHP and phosphoric acid concentrations, and found to be mainly controlled by diffusion in the single drop. Further, it was found that CYANEX-921 can substitute TOPO to synergise the extraction of UO22+ by HDEHP. © 1997 SCI.

Liquid-liquid extraction of uranium from phosphoric acid by HDEHP-CYANEX-921 mixture

The need exists for preconcentration of trace and ultratrace amounts of uranium from environmental, geological and biological samples. The adsorption of uranium on various solids is important from the purification, environmental, and radioactivity waste disposal points of view. A method is described for the determination of traces of uranium using first-derivative spectrophotometry after adsorptive preconcentration of uranium on activated carbon. Various parameters that influence the adsorptive preconcentration of uranium on activated carbon, viz., pH, amounts of activated carbon and time of stirring and interference of metals have been studied. First-derivative spectrophotometry in conjunction with adsorptive preconcentration of uranium on activated carbon is used for determining uranium at concentration levels down to 20ppb (w/v).

Collection/concentration of trace uranium for spectrophotometric detection using activated carbon and first-derivative spectrophotometry

A new poly(vinyl chloride) (PVC) electrode for Cs+ ion based on Cs‐12‐molybdophosphate (Cs‐12‐MPO) as a membrane carrier is prepared and characterized. The electrode exhibits a linear response with slope of 46.5 ± 1 mV/decade within the concentration range of 1.0 × 10−5–1.0 × 10−1 mol L−1 Cs+ ion. The limit of detection was 3.0 × 10−6 mol L−1. The proposed electrode shows a good selectivity for Cs+ ion over a wide variety of other metal ions and could be used in the pH range of 4.0–6.0. It has a relatively fast response time less than (30 s) and can be used for at least three weeks without any considerable divergence in potentials. The proposed electrode is applied as a sensor for the determination of Cs+ ion concentration in some samples. The results show a good correlation with the data obtained by atomic absorption spectrometric method. The average recovery obtained is 92 ± 0.5% with a standard deviation of 1.2%.

A New Cesium Ion Selective Graphite Rod Electrode Based on Cs‐Molybdophosphate

A new lead(II)-selective electrode has been developed based on bis(acetylacetone)-p-phenylenediamine-lead(II) [LPb(NO 3 ) 2 ]H 2 O complex ionophore as a sensing material, dioctylphthalate (DOP) as a solvent mediator and PVC as a matrix. This electrode exhibits a linear Nernstian response over the concentration range of 1 x 10 -5 - I x 10 -1 mol 1 -1 of Pb(II) cation, with a cationic calibration slope of 30.0 ± 0.2 mV/concentration decade and a detection limit of 2 x 10 -6 mol 1 -1 (0.40 ppm). It has a fast response time and can be used for a period of 2 months without any divergence in potentials. The proposed electrode reveals a good selectivity for Pb(II) over a wide variety of other tested cations and could be used in the pH range of 4 - 8. It was successfully used for direct determination of Pb(II) concentration in some samples. The obtained results show a good agreement with those obtained by an atomic absorption spectrometric method. The average recovery obtained is 96.5 ± 0.5% with standard deviation of 1.2% (n = 8).

Sohair A. El-Reefy

Papers

Purification of wet phosphoric acid from ferric ions using modified rice husk

Liquid-liquid extraction of uranium from phosphoric acid by HDEHP-CYANEX-921 mixture

Collection/concentration of trace uranium for spectrophotometric detection using activated carbon and first-derivative spectrophotometry

A New Cesium Ion Selective Graphite Rod Electrode Based on Cs‐Molybdophosphate

A new lead(II)-selective PVC-coated graphite rod electrode based on a Schiff base complex.