A Study of Silica Separation in the Production of Activated Carbon from Rice Husk in Viet Nam

Environmental pollution due to mismanagement of the waste from rice production is a serious problem in agricultural countries where rice cultivation occupies the largest proportion of the crops produced, including in Viet Nam. At the same time the use of activated carbon as an adsorption agent for water or gas purification is rapidly increasing due to the development of industry and technology in the developed countries. In this paper we consider the process of separating silica from charcoal, which is an important step in the production of activated carbon from rice husks in Viet Nam. The efficiency of the process rises with increasing temperature up to 133 °С, the ratio of alkali/charcoal up to 0.6 and sodium hydroxide concentration up to 6 M as well. A regression equation has been obtained, which allows describing the influence of the parameters on the degree of silica separation from the carbon. Under optimal values of process parameters, the efficiency reaches up to 95.6%

Production of activated carbon from rice husk Vietnam

This work is dedicated to the production of activated carbon from rice husk from Delta of the Red River in Viet Nam. At the first stage, carbonization of a rice husk was carried out to obtain material containing 43.1% carbon and 25 % silica with a specific surface area of 51.5 m{2}/g. After separating of silica (the second stage), the specific surface area of the product increased to 204 m{2}/g and the silica content decreased to 1.23% by weight as well. The most important stage in the formation of the porous structure of the material is the activation. The products with the high specific surface area in the range of 800-1345 m{2}/g were obtained by activation of carbonized product with water vapour or carbon dioxide at temperatures of 700 °C and 850 °C, with varying the flow rate of the activating agent and activation time. The best results were achieved by activation of carbon material with water vapour at the flow rate of 0.08 dm{3}/min per 500 g of material and the temperature of 850 °C

The Application of Ammonium Hydroxide and Sodium Hydroxide for Reagent Softening of Water

The calcium carbonate crystallization from aqueous solutions in the presence of alkali additives such as sodium hydroxide and ammonium hydroxide has been researched. It is found CaCO[3] crystallizes predominantly in the modification of aragonite in the presence of ammonium hydroxide. The calcium carbonate formation rate in an alkaline medium and the gaseous reaction products due to sorption of gas bubbles on crystal surfaces, affect the aragonite structure formation. It is shown use of ammonium hydroxide for water treatment can solve two urgent tasks such as water softening and exclusion sediment of deposits on the equipment surfaces by a calcium carbonate crystallization in the form of aragonite

Electrochemical synthesis of nickel-aluminium oxide system from metals obtained by ore processing

Separate and combined electrochemical oxidation of aluminium and nickel has been conducted by alternating current of industrial frequency. Concentration increase of electrolyte solution (sodium chloride) in the range from 3 to 25 wt. % and current density from 0.5 to 1.5 A/cm{2} was found to result in the increasing metal oxidation rate, excluding aluminium oxidation which oxidation rate is independent of the electrolyte solution concentration. At the current density of 1.5 A/cm{2} the products of separate oxidation of nickel and aluminium are nickel oxyhydroxides, nickel hydroxides and aluminium oxyhydroxide (boehmite), respectively. In addition to these compounds, the nickel-aluminium oxide hydrate is included in the products of nickel and aluminium co-oxidation. Its content grows with the increasing electrolyte solution concentration. Varying the concentration and current density within the limits indicated, the nickel-aluminium oxide system with nickel oxide content from 3 to 10 wt. % is produced

AC Electrochemical Copper and Aluminum Oxidation in Sodium Acetate Solutions

Electrochemical copper and aluminum oxidation using alternating current of industrial frequency was carried out in an aqueous sodium acetate solution. Simultaneous oxidation of metals accelerates copper oxidation, but does not significantly influence the aluminium oxidation rate. It results in the preparation of the copper-aluminum oxide system with a high content of copper oxide (up to 70 wt %). High energy consumption due to the voltage loss to overcome the resistance of the oxidation product layer on the electrode surface considerably limits the process and its product application. Furthermore, the chemical aluminum oxidation in alkaline medium of an aqueous sodium acetate solution instead of electrochemical one does not result in the power-saturated, nanosized metal oxide formation. The results obtained do not only underline the new technology of nanomaterial production, but also allow scientists to consider the mechanisms of the metal oxidation AC-process

Solution Transformation of the Products of AC Electrochemical Metal Oxidation

Electrochemical oxidation of copper and aluminium using alternating current of industrial frequency results in the formation of non-equilibrium products. Their transformations during the ageing in sodium chloride solutions of different concentrations have been considered. According to X-Ray diffraction confirmed by TG/DSC/DTG analysis, irrespective of solution concentration, the ageing products consist of aluminium oxyhydroxide (boehmite, AlOOH), copper-aluminium carbonate hydroxide hydrate (Cu-Al/LDH) and copper chloride hydroxide (Cu[2](OH)[3]Cl). The increase of the solution concentration leads to Cu[2](OH)[3]Cl formation and makes difficulties for metal oxide carbonization to Cu-Al/LDH. Ageing in highly diluted solution contributes not only to Cu-Al/LDH formation but also boehmite hydration that is verified by IR-spectra. The pore structure characteristics have been also discussed. They do not significantly depend on phase composition and vary in ranges of 161.2-172.6 m{2}/g (specific surface areas), 0.459-0.535 cm{2}/g (total pore volumes). Pore size distributions reveal that a pore structure is predominantly formed by pore with the sizes from 3 to 22°nm; 3.6°nm is the size of pores with the largest pore volume

Characterization of Copper and Aluminum AC Electrochemical Oxidation Products

Non-equilibrium electrochemical metal oxidation is one of the methods to obtain the power-saturated nanosized metal oxides. AC electrochemical separate copper and aluminum oxidation in an aqueous sodium chloride solution is performed. It results in the phase transformations of the obtained copper (I) oxide and boehmite during the storing in solution. Phase composition, pore structure characteristics and morphology of the products are considered. Their pore structure is preferably formed by mesopores. Carbonate ion adsorption of metal oxides/oxyhydroxides is due to their high affinity. The contamination of the power-saturated nanosized products of electrolysis with carbon-containing impurities is not a problem because some undesirable compounds may be removed by heat treatment, but others do not negatively affect the operating performance. Product of AC electrochemical copper oxidation is characterized by particle shape anisotropy (spindle-shaped particles of copper oxide and copper carbonate hydroxide wire bundles) that positively affects the some properties. The product of AC electrochemical aluminum oxidation has a flower-like structure

Joint Destruction of Cadmium and Copper at Alternating Current Electrolysis in Sodium Hydroxide Solution

The dependence of the metal oxidation rate on the current density and temperature of joint destruction in sodium chloride was studied. It is established that the dependence of the oxidation rate of copper is linear and generally do not differ from the dependencies established at individual oxidation of copper in the solution of sodium chloride with concentration 46.5% wt. In contrast to the oxidation rate of copper, the oxidation rate dependence of cadmium has extreme character and the oxidation rate of cadmium at its joint oxidation of copper increased in 2-3 times indicating that the mutual influence of electrodes at the electrochemical process with alternating current. Thus, the obtained dependences can predict operating electrolysis parameters a obtain copper-cadmium oxide system of the given composition

The Porous Structure of Copper-cadmium Oxide System Prepared by AC Electrochemical Synthesis

The porous structure of nanoparticles of copper-cadmium oxide system prepared by AC electrochemical synthesis in sodium chloride with a concentration of 3, 15, 25 wt. % has been studied. The obtained data indicate that at a higher current density and sodium chloride concentration of 3% wt. in the electrochemical oxidation of cadmium and copper products are formed with the structure of mesopores and channels. In this case, the specific surface area has the greatest value (19.4 m{2}/g) and a maximum pore volume (0.0778 cm{3}/g). Thus, the obtained data allow predicting the operating parameters of the electrolysis to obtain a copper - cadmium oxide system of a predetermined porous structure