Caustic Soda Solution Research Articles

Scientific opinion on the safety assessment of the following processes based on Modified Hybrid URRC UnPET technology used to recycle post‐consumer PET into food contact materials “CLR rPET”, “PET to PET” and “Veolia”

This scientific opinion of EFSA Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids deals with the safety assessment of the recycling processes CLR rPET, PET to PET, and Veolia (EU register numbers RECYC029, RECYC053 and RECYC071) which are all based on the same modified hybrid URRC UnPET technology. The decontamination efficiency was demonstrated using the same challenge test. Through this technology, washed and dried PET flakes are coated with a solution of caustic soda and pre-dried in a stirred reactor under vacuum and then transferred to a rotary oven under dry air counter flow. The Panel concluded that the chemical etching of flakes, the drying of the flakes and the decontamination in the rotary oven are the critical steps that determine the process decontamination efficiency. The operating parameters to control the performance of these critical steps are dosing of caustic soda solution, the temperature of dry air, the temperature and the residence time of the flakes in the rotary oven. It was demonstrated by the challenge test that the recycling processes under evaluation are able to ensure that the level of migration of potential unknown contaminants into food is below a conservatively modelled migration of 0.1 μg/kg food. Therefore, the Panel considered that the recycling processes based on modified hybrid URRC UnPET technology are able to reduce any foreseeable accidental contamination of the post-consumer food contact PET to a concentration that does not give rise to concern for a risk to human health. The Panel concluded that the recycled PET obtained from the processes CLR rPET, PET to PET and Veolia intended for the manufacture of materials and articles for contact with all types of foodstuffs for long term storage at room temperature, with or without hotfill is not considered of safety concern.

Development of 216L for Conservation of Nickel & Molybdenum and its Application in Sugar Refinery Instead of 316L

Development of an austenitic Fe-Cr-Mn-Ni-Mo-Cu-N alloy 216L to substitute AISI 316L for saving a part of expensive nickel and molybdenum is described. Nickel content is reduced by 40% and molybdenum by 25% with the help of nitrogen, manganese and copper additions. Corrosion tests in boiling solutions in a variety of acidic media including oxalic, nitric, phosphoric, sulfuric and chromic acids and polarization curves in acidic and chloride environment indicate similar behaviour of both grades. There is also striking similarity in pitting corrosion resistance and inter-granular corrosion resistance of the two alloys as per ASTM G-48 and ASTM A262 respectively. Both alloys exhibit excellent resistance to any staining in prolonged salt spray test. Produced by conventional EAF-AOD-CC-Steckel Mill route, the alloy exhibits surface quality comparable to AISI 316L in both hot and cold rolled conditions. Like 316L, it is equally amenable to fabrication and welding. Higher yield strength of 216L confers potential for material saving in use as compared to 316L. In the process of extracting refined sugar from raw sugar a number of chemicals are used. Accumulated scale from the equipments is periodically removed by using hot solutions containing caustic soda and soda ash followed by rinsing in solutions containing dilute hydrochloric acid and finishing with water rinse. The steel generally used is 316L and based on comparative performance of 216L this new alloy was successfully used in sugar refinery columns where it is subjected to periodic cleaning by hot salt & caustic soda solution and hot dilute hydrochloric acid.. Key words: nickel conservation, 216L austenitic stainless steel; corrosion resistance, sugar refinery

Treatment of petroleum refinery sulfidic spent caustic wastes by electrocoagulation

In order to protect environment and to recover caustic soda solution, electrocoagulation technology was used to remove sulfide and organics from refinery spent caustic wastes. The performance of elctrocoagulation in the removal efficiency of sulfide and organic compounds was investigated. Several working parameters, such as solution pH, current density and electrode nature were studied in an attempt to achieve a higher removal capacity. The optimum electrocoagulation time, initial pH, current density were found to be 30min, pH 9 and 21.2mAcm−2 for initial sulfide concentration of 34,517mgL−1 and COD of 72,450mgL−1 respectively. Under the optimum conditions established, removal efficiency of sulfide and organics expressed as COD was greater than 80%. Furthermore, successive electrocoagulation technique (dual EC units) yields a very effective (>95%) removal of residual compounds and heavy metals in basic aqueous medium. The method was found to be highly efficient and relatively fast compared to conventional existing techniques such as chemical oxidation, precipitation or by neutralisation.

Simulation of the Effect of Various Operating Parameters for the Effective Separation of Carbon Dioxide into an Aqueous Caustic Soda Solution in a Packed Bed Using Lattice Boltzmann Simulation

Nowadays, reduction of the carbon footprint in the environment is one of the most challenging issues, and thus several technologies have been adopted for the effective arrest of carbon dioxide (CO2...

Electrophoretic Growth of PbTiO3 Nanotubes

Sol-gel electrophoresis technique has been used as a usual method merely for preparing PbTiO3 thin film and nanowires with high quality and more condense layers. In this research, initially we used this technique to grow PbTiO3 nanotubes in porous anodic alumina template channels. Firstly, templates are prepared via two-step anodizing of pure aluminum foils in phosphoric acid. Then, the templates were filled with a highly stabilized PbTiO3 sol prepared and we used titanium tetra-butoxide and lead acetate trihydrate as precursors. An electric field (DC) was applied to drive the sol into the template channels. Nanotubes were formed after the etching of the porous template with 5 wt.% caustic soda solution. The heat treatment condition was evaluated based on the simultaneous thermal analysis results of the prepared and crystallization of the tetragonal perovskite structure by the X-ray diffraction of the grown nanotubes. Scanning electron microscopy investigations showed that close-packed PbTiO3 nanotubes have been grown in the template channels.

Heating Assist System for Liquid Tank Using Shallow Geothermal Energy via Heat Pipe BACH

This study aims to develop a heating assist system for liquid tanks by using shallow geothermal energy via a new type of heat pipe named Bubble-Actuated Circulating Heat pipe (BACH). In this system, BACH transports heat from shallow underground (temperature remains constant at around 15 °C in Fukui) to the liquid of caustic soda solution (49 wt%, freezing point is about 5 °C) preserved in the tank. From a previous simplified small-scale experiment, we concluded that BACH could warm the liquid to some extent in winter. In this report, experimental results of field tests are demonstrated where 10 m3 tank equipped with an electric heater as an auxiliary heater was tested and five sets of BACH were installed. As a result, this system could warm the liquid at about 7 °C only by BACH without electricity under the experimental conditions tested.

A233 ヒートパイプBACHによる浅層地中熱利用液体タンク保温補助システム(OS2 再生可能エネルギー(5))

This study aims to develop a heating assist system for liquid tanks by using shallow geothermal energy via a new type of heat pipe named Bubble-Actuated Circulating Heat pipe (BACH). In this system, BACH transports heat from shallow underground (temperature remains constant at around 15 ℃ in Fukui) to the liquid of caustic soda solution (49 wt%, freezing point is about 5 ℃) preserved in the tank. From a previous simplified small-scale experiment, we concluded that BACH could warm the liquid to some extent in winter In this report, experimental results of field tests are demonstrated where 10 m^3 tank equipped with an electric heater as an auxiliary heater was tested and five BACHs were installed. As a result, this system could warm the liquid at about 7 ℃ only by BACH without electricity.

A contribution to the experimental determination of mass transfer in counter-current flow through ceramic sponges

Ceramic sponges were explored with established test systems from literature concerning their mass transfer coefficients and effective interfacial area in counter-current flow. Absorption of carbon dioxide diluted with air in caustic soda solutions as well as desorption of carbon dioxide from water into air are used. An analysis of the measurement methods concerning reliability of the results for sponges was performed. The focus was set on effects like wetting of the sponge structure, which have to be taken into account for any further investigation of mass transfer characteristics in sponges.

New methods of the improvement of metal corrosion resistance through surface impregnation with anode electrolyte heating

It is shown that the use of the electrolyte composition developed in this work allows one to reduce by almost twice the carbon content in the surface layer of steel 45 and, with the introduction of an additional operation after the electrolytic heating (oxidation in an aqueous solution of caustic soda with a concentration of 50–100 g/L), to reduce the corrosion rate almost by a factor of two. It is also established that processing in another electrolyte formulated in the course of the research leads to the reduction of the corrosion rate of electrolytic iron coverings by more than 2 times.

Observation of transcrystalline growth of PLA crystals on sisal fibre bundles and the effect of crystal structure on interfacial shear strength

Hot-stage microscopy was used to characterise crystal growth at the interface between sisal fibre bundles and a polylactic acid (PLA) matrix in order to better understand the mechanical properties of sisal fibre–PLA composites. Cooling rates and crystallisation temperatures and times were varied to influence crystalline morphology at the interface. Single sisal fibre bundles were evaluated in their as received state or treated with 6 wt.% caustic soda solution for 48 h at room temperature. A microbond shear test was used to characterise the shear strength of the interface as a function of fibre surface treatment. These tests were performed on sisal fibre bundles carefully embedded in flat films of PLA supported on card mounts. Fibre bundles in a PLA matrix were cooled from 180 °C at rates from 2 to 9 °C/min and then crystallised isothermally. For as received fibre bundles uneven growth of PLA spherulites occurred at all cooling rates and crystallisation temperatures. For caustic soda treated fibres, uneven spherulitic growth was observed at crystallisation temperatures at and above 125 °C. In contrast, transcrystalline growth was observed for samples cooled to 120 °C at cooling rates from 2 to 6 °C/min and then allowed to crystallise. The microbond shear strengths of untreated and caustic soda treated fibre bundles were evaluated using Weibull statistics and the caustic soda treated fibres exhibited higher interfacial shear strengths in comparison to untreated fibres, reflecting the development of a transcrystalline layer at the fibre to matrix interface.

Effect of Aqueous Extracts of Bitter Leaf Powder on the Corrosion Inhibition of Al-Si Alloy in 0.5 M Caustic Soda Solution

The effect of bitter leaf (Vernonia amygdalina) extract as an inhibitor for aluminium silicon alloy in 0.5 M solution of caustic soda using weight loss method has been investigated. The alloy of composition 9% Si and 91% Al was sand cast at the Foundry Shop of the National Metallurgical Development Centre, Jos, Nigeria. The cast alloy was cut and machined to corrosion coupons and immersed into 0.5 M NaOH solution containing varying inhibitor concentrations (0.1%, 0.2%, 0.3%, 0.5% v/v) within a period of fifteen days. From the result, it was found that the adsorption of Vernonia amygdalina reduced the corrosion rate of this group of alloy in the alkaline medium. The inhibitive action of this plant extract was explained using inhibition efficiency and degree of surface coverage. The most suitable inhibitor concentration was found to be 0.5% with inhibition efficiency of 87%. The mechanism of inhibition is by physical adsorption and the adsorbed molecules of the inhibitor lies on the surface of the alloy blocking the active corrosion sites on the alloy, hence, giving the alloy a higher corrosion resistance in the studied environment.

Chemical Treatment to Recover Molybdenum and Vanadium from Spent Heavy Gasoil Hydrodesulfurization Catalyst

Large quantities of spent hydrodesulfurization (HDS) catalysts are available from petrochemical industry. Disposal of spent catalyst is a problem as it falls under the category of hazardous industrial waste due to its vanadium concentration. Most of these catalysts are usually supported on alumina containing a variable percentage of elements such as nickel or molybdenum. Hence these catalysts contain environmentally critical, and economically valuable metals such as molyb denum, vanadium, and, nickel. In this paper, a spent HDS catalyst was treated with caustic soda solution. Parameters such as temperature, time, and NaOH solution concentration have been studied thoroughly, in order to settle the appropriate conditions for the maximum recovery of molybdenum and vanadium. Under the best leaching conditions (20 %w NaOH, room temperature, 2 h) about 95% recovery of Mo and V was achieved, and the recovery of nickel obtained was of 99% in the form of NiAlO4.

Effect of exposure time on the morphology of corrosion on high chromium white cast iron in high temperature caustic solutions

AbstractHigh chromium white irons are important candidate materials for use in alumina refineries to combat wear and corrosion. The effect of exposure time on the formation of oxide films was studied in a 23% Cr white cast iron exposed at 260 °C in 110 g/l caustic soda solutions. It was found that whilst well‐formed octahedral M(II)O.M(III)2O3 spinel type oxides initially formed and spread across the surface of the material, these were gradually replaced by a background oxide with a higher Cr/Fe ratio and the morphology of the octahedral crystals became less well formed. Also, the oxidation was found to be predominantly in the matrix material, leaving carbide particles unsupported on the surface and in the later stages, significant corrosion was found along the carbide/matrix phase boundary.

Hydrodynamics of gas–liquid Taylor flow and liquid–solid mass transfer in mini channels: Theory and experiment

Hydrodynamics of Taylor (slug) flow in horizontal capillary with an inner diameter of 0.92 mm in water–air and glycerol solution–air systems was studied. Experimental data of bubble velocity, dynamic gas hold-up and void fraction were compared with values that were calculated by proposed earlier mathematical model of slug flow in capillary. This model is in a good agreement with experimental data in the range of capillary numbers between 0.05 and 0.12. Also liquid–solid mass transfer coefficient for slug flow and homogeneous flow was experimentally obtained in horizontal capillary with an inner diameter of 2.26 mm and 2.76 mm in a caustic soda solution–air system.

An unconventional method for the recovery of caustic soda from spent Al-rich pickling solutions

This work presents an unconventional procedure for the recovery of spent Al-rich caustic soda solutions from the pickling of dies for the production of aluminium extrusions. Caustic soda was regenerated at roughly 70%, by precipitating aluminate, after addition of a silica source, in the form of zeolite A, a microporous material that is widely used in many technological sectors. It was shown that the process is reliable and can be repeated for several cycles, provided the concentration of the caustic soda solution is suitably restored. The by-product obtained, zeolite A, proved to be a high-grade material with performance as a cation exchanger and physical sorbent that is certainly comparable to that reported in literature (e.g., cation exchange capacity equal to 5.14 meq g −1 vs. 5.48 meq g −1 and water vapour adsorption capacity of 26.5% vs. 27.6% at 16 torr and 298 K). The economics of the process, although not examined yet, would appear generally favourable, considering that zeolite A is a valuable by-product which widely covers the costs for the recovery of the spent solutions. There are, therefore, significant prospects for the use of zeolite A, particularly as a builder in detergent formulation.

Recycling of aluminum and caustic soda solution from waste effluents generated during the cleaning of the extruder matrixes of the aluminum industry

Anodising industries use a concentrated caustic soda solution to remove aluminum from extruder matrixes. This procedure produces very alkaline effluents containing high amounts of aluminum. The work reported here was focussed on recycling aluminum, as aluminum hydroxide, from these effluents and regenerating an alkaline sodium hydroxide solution. Briefly, the method comprises a dilution step (necessary for reducing the viscosity of the effluent and allowing the subsequent filtration) followed by a filtration to eliminate a substantial amount of the insoluble iron. Then, sulphuric acid was added to neutralize the waste solution down to pH 12 and induce aluminum precipitation. The purity of the aluminum salt was improved after washing the precipitate with deionised water. The characterization of the solid recovered, performed by thermogravimetric analysis, Fourier transform infrared spectroscopy and X-ray diffraction, indicated characteristics typical of bayerite. The proposal method allowed recovering 82% of the aluminum present in the wastewater with high purity (99.5%). Additionally, a sufficiently concentrated caustic soda solution was also recovered, which can be reused in the anodising industries. This procedure can be easily implemented and ensures economy by recycling reagents (concentrated caustic soda solution) and by recovering commercial by-products (aluminum hydroxide), while avoiding environmental pollution.

The Use of Ozone in a CIP System in the Wine Industry

This study tested the efficacy of ozone in a CIP system of a wine industry, for that, a hose that transported wine was submitted to the following treatments: ozonated water at 28 ± 1 °C (in concentrations of 0.38 and 1.03 ppm for one, five and nine minutes); hot water (85 ± 1 °C for 15 minutes); peracetic acid (0.3% for 15 minutes); and a caustic soda solution (2%) with peracetic acid (0.3% for 15 minutes). The results indicate that the use of ozonated water is more effective than the isolated use of peracetic acid and the combined use of soda and peracetic acid.

Study of an Evaporation System for Sodium Hydroxide Solution

The textile industry in Bangladesh uses a substantial quantity of caustic soda (sodium hydroxide) to clean and prepare fabrics for dyeing. In all textile mills dealing with finishing, particularly with the mercerizing of cotton and mixed cotton fabrics, dilute caustic soda solutions come out as effluent from mercerizing unit. Caustic soda is expensive and its disposal without neutralization is unacceptable. A considerable amount of caustic soda can be saved if the dilute solution leaving the mercerizing step can be collected, concentrated and recycled. The concentration of the dilute caustic soda solution can be carried out by means of evaporation. A single effect evaporation system to concentrate the dilute sodium hydroxide solution was constructed and operated. The operating results confirm the economic viability of such recovery scheme.Journal of Chemical Engineering Vol.ChE 24 2006 35-36

Coating composition, weld parameter and consumable conditioning effects on weld metal composition in shielded metal arc welding

Pipeline construction has been moving towards the use of higher strength low carbon steels as these become available. In order to achieve the required high strength and toughness to match those of the parent pipe, girth weld metals have to rely mostly on their composition. The aim of the present study was to characterise the influence of the consumable chemistry and moisture content, and the welding parameters on the composition of weld metals produced by E8010 and E9010 shielded metal arc (SMA) cellulosic consumables. The alloying compounds in the consumable coating were isolated using a caustic soda solution, analysed with electron backscattered diffraction and identified as a variety of oxides. Making use of a mechanised SMA welding machine, the effect on weld metal alloying element contents of the welding conditions was evaluated. Smaller welding arc voltages and lower consumable coating moisture content produced weld metals with richer chemistry. The element transfer mechanisms from the consumable coating to the weld metal are also discussed.

Performance and effects of polymeric membranes on the dead-end microfiltration of protein solution during filtration cycles

A systematic study investigating the effect of membrane material and morphology on the filtration-cycle based on performance of three microfiltration membranes employed for filtering feed solution of Bovine Serum Albumin with yeast suspension has been carried out in dead-end filtration mode. The effects of operating conditions, like feed solution pH, transmembrane pressure (TMP), and membrane cleaning methods have been studied to establish a possible relationship with membrane fouling and to reduce the fouling that occurs during filtration. It was found that filtration resistance increases for the selected membranes with an increase in pH of the feed solution. An increase in TMP increases the permeate flux; however, the effect is not linear due to cake compression at higher TMP. The performance based on the filtration cycle is evaluated, and potential cleaning solutions to restore the permeate flux of filtration after several filtration cycles are identified. Scanning electron microscopy images demonstrate the experimental findings. The expanded polytetrafluoroethylene membrane flushed with caustic soda solution is found to be the most suitable and efficient membrane for microfiltration without significant reduction in flux and protein transmission, even after several filtration cycles.