Study Of Reutilization Research Articles

Feasibility study of utilizing Autoclaved Aerated Concrete (AAC) waste for the production of cold bonded lightweight artificial aggregate using high volume fly ash (HVFA) binders

Autoclaved Aerated Concrete (AAC) is a popular construction material used for partitions and insulation in buildings. At the end of its service life, AAC (Autoclaved Aerated Concrete) will be demolished and subsequently disposed of in landfills, thereby creating depository problem. Therefore, the study of reutilization and recycling of AAC waste is imperative. Artificial aggregate production can be an alternative to the reutilization of AAC waste. This paper assesses the feasibility of using Autoclaved Aerated Concrete Powder (AACP) waste as a raw material for the production of artificial aggregate and investigate its physico-mechanical properties. The investigation incorporates the comparison of cement-based binder with high-volume fly ash (HVFA) binder with different replacement levels of cement. The study uses image analysis based on photographic, optical microscopic, and scanning electron microscopy (SEM) images, to describe the porosity of the aggregate. The results show that the AACP aggregates with both cement and HVFA binders meets the current industry requirement for density and cylinder crushing strength as lightweight artificial aggregate. The appropriate binder content lies between 30 % and 40 %. The best cement to fly ash ratio in HVFA binder is determined to be of 1:1 with 50 % replacement of cement with fly ash. Image analysis showed that the porosity largely affected the properties of the AACP aggregate such as density and water absorption. However, further investigation into the reducing high-water absorption of AACP aggregates is necessary to improve their overall quality.

Recyclable photocatalytic composites based on natural hydrogels for dye degradation in wastewaters

Two polysaccharide-based hydrogels: agarose and chitosan have been used to shape pieces containing micrometer anatase (TiO2). The degradation of Methylene Blue and Rhodamine, two pigments frequently found in textile industry wastewaters, has been employed to test the photocatalytic capacity of such composites. These experiments were carried out indoor under an artificial light that simulates the solar spectrum. An initial test demonstrated that the agarose-containing pieces showed a degradation superior to that observed when chitosan or chitosan/agarose mixtures were used to aggregate the TiO2 powders. The following parameters: pieces geometry, surface exposition, porosity and anatase content were optimized to reach the highest degradation capability. The so obtained materials, subjected to long term and reutilization studies, showed that high degradation rates were maintained even under such conditions. Taking this into account, it can be stated that these low cost and recyclable pieces have a great potential applicability for actual wastewater depollution procedures.

Meso-porous activated carbon from lignite waste and its application in methylene Blue adsorption and coke plant effluent treatment

Coke plant wastewater contains many toxic pollutants such as phenol, cyanide, and ammonia, etc., handling and disposal of which has a significant impact on the environment and human health. A novel adsorbent based on lignite extraction waste was prepared and its effect on the removal of simulated methylene blue, phenol and colour (ortho, para-benzo quinone) from real coking wastewater was investigated. Lignite waste (residue) after humic acid separation has a significant quantity of oxidized functional groups along with residual KOH, which makes it suitable for the preparation of activated carbon with high surface area. Since hydrothermal extraction breaks coal-mineral-pore aggregate, the separation efficiency of ash-bearing minerals improved, 11 % ash coal prepared from the residue with 81.6 % yield. Prepared activated carbon from low ash residue has a mesoporous surface (49.8 nm pore size), 0.554 cm3/g of total pore volume, and 980 m2/gram BET surface area. The adsorption kinetics followed pseudo-second order (R2 = 0.984) for methylene blue, pseudo-second-order (R2 = 0.978) for phenol, and pseudo-first-order (R2 = 0.935) for colour adsorption. Adsorption isotherm at equilibrium shows a maximum adsorption capacity of 120 mg/g for methylene blue, 20.49 mg/g for phenol and 588.23 PtCo/g for colour. The adsorption isotherm was in good agreement with Langmuir isotherm (R2 = 0.989−0.994) compared to Freundlich model (R2 = 0.924−0.982). The presence of negatively charged surface favours the uptake of cationic groups. Apart from phenol and colour, the adsorbent can remove total organic carbon (TOC) by 93.6 % and thiocyanide by 6.7 %. Adsorbent reutilization studies show that, the regenerated adsorbent by thermal treatment can be used for 3 cycles.

Immobilization and controlled release of β-galactosidase from chitosan-grafted hydrogels

Chitosan-grafted hydrogels were employed for immobilization and controlled released of β-galactosidase. These hydrogels containing immobilized enzymes were employed to simulate the production of lactose-free food and controlled release of β-galactosidase into lactose-intolerant individuals. The degree of swelling, efficiency of immobilization (i.e., fractional uptake of enzyme), and controlled release were studied as a function of pH and temperature. The degrees of swelling decreased in acidic media: 49.4g absorbed water per g hydrogel at pH 7.0, and 8.4g absorbed water per g hydrogel at pH 3.5. The immobilization efficiency was 19%, indicating that chitosan-grafted hydrogels are promising matrices for enzyme adsorption and immobilization. Cyclic experiments reveal that chitosan-grafted hydrogels containing immobilized enzymes can be reused several times without introducing additional enzyme prior to each cycle. There is no significant decrease in the activity of the immobilized enzyme during reutilization studies. All results were conducted in triplicate by considering t-tests at a 95% significance level. Analysis of β-galactosidase activity and controlled release reveals that chitosan-grafted hydrogels containing immobilized enzymes are useful for the production of lactose-free food and controlled enzyme release with high performance.

Highly concentrated emulsion with a cubic liquid crystal as the external phase: characterization and obtaining of meso/macroporous material

High internal phase ratio emulsions (HIPRE) or highly concentrated emulsions are characterized by their large internal phase volume.The nature and concentration of surfactant affects several features of the final emulsion, such as stability, droplet size and structure of the external phase. Therefore, an ordered external mesophase (structure of liquid crystal) can be obtained. The present work studies the influence of composition and preparation variables on the final properties of HIPRE with an external phase formed by a bicontinuous cubic liquid crystal. The studied outputs variables were droplet size, stability and rheological parameters as yield stress, viscosity at a fixed shear rate and the plateau value of the storage modulus. O/W HIPREs were prepared with a decane/brij 35/water system. Once the emulsions were characterized the meso/macroporous material was obtained. In order to prepare the materials, the emulsions were formed by incorporating the catalyst of the reaction (HCl) in the continuous phase. When the emulsions were formed, tetraethylorthosilicate (TEOS) was added as a silica source In order to optimize the production process a study of reutilization and recovery of some of the raw materials (i.e: the surfactant and the EtOH used) was done.DOI: http://dx.doi.org/10.3126/jncs.v30i0.9374Journal of Nepal Chemical Society Vol. 30, 2012 Page: 87-96 Uploaded date: 12/19/2013

Binol derivative ligand immobilized onto silica: Alkyl-cyanohydrin synthesis via sequential hydroformylation/heterogeneous cyanosilylation reactions

A new 6,6′-dicarboxyl-BINOL type ligand, was synthesized and anchored onto a aminated silica. Full characterization of the solids was carried out by means of thermogravimetry/differential scanning calorimetry, N2 adsorption, infra red and UV–vis diffuse reflectance spectroscopy techniques. Comparative studies between homogeneous versus heterogeneous catalytic cyanosilylation reactions of aldehydes were carried out, and similar activities were obtained. Furthermore, an efficient sequential process to promote the hydroformylation of 1-octene into nonanal followed by in situ cyanosilylation of the aldehyde, catalyzed by titanium immobilized BINOL derivative, is described. Reutilization studies of cyanosilylation catalyst revealed that the new titanium immobilized catalyst could be reused with 25% loss of activity after 3 reuses.

Activated carbons treated with sulphuric acid: Catalysts for catalytic wet peroxide oxidation

Different liquid phase thermal treatments were applied to a commercial activated carbon (Norit ROX 0.8) in order to produce modified activated carbons with varying surface chemistry and increased acidic character. Chemical characterization of the prepared materials includes determination of the point of zero charge and evaluation of the concentration and nature of acidic and basic surface functionalities by acid/base titrations and temperature programmed desorption. The prepared materials were used as catalysts in the catalytic wet peroxide oxidation of the acid dye Chromotrope 2R in order to assess their removal efficiency. The relationship between the surface chemistry and efficiency for dye removal is discussed. As expected, decreasing acidity of the catalysts surface will correlate with increasing dye conversion. Unexpectedly, treatment with sulphuric acid leads to a very high yield of dye removal which falls out of the previous correlation. This was explained in terms of the introduction of sulphur containing groups on the carbon surface, which promotes the surface interaction between the pollutant and hydrogen peroxide: higher production of hydroxyl radicals close to the pollutant leads to improved dye removal. In addition, reutilization studies show that the catalyst prepared by sulphuric acid treatment is able to keep its performance in successive runs.

Reutilization of Iron in Anemia Complicating Malignant Neoplasms

Abstract A study of reutilization of iron by means of Fe59-tagged hemoglobin solution given to normal individuals yielded a rate of reutilization of 70 per cent or more, evidence perhaps that the active storage pool of iron at a given moment is not larger than the plasma iron compartment. Reutilization of iron in patients with anemia complicating malignancy disease has shown a significant decrease which correlates well with the severity of the anemia.