Preparation and Characterization of Nanozeolite NaA from Rice Husk at Room Temperature without Organic Additives

Nanozeolite NaA was synthesized by the hydrothermal method with silica extracted from rice husk as silica source. Amorphous silica with 87.988 wt%  SiO2 was extracted from rice husk ash by a suitable alkali solution. The effect of the crystallization time and the ratio of Na2O/SiO2 on the properties of the final product was investigated. The synthesized nanozeolite was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) techniques, and Brunauer-Emmett-Teller (BET) method. Results revealed that the crystallization time and alkalinity have significant effects on the structural properties of nanozeolite. Nanocrystals NaA with crystal sizes ranging from 50 to 120 nm were synthesized at room temperature with 3 days aging, without adding any organic additives

Evaluating the Feasibility of Poly (3-hydroxybutyrate-co-3-hydroxyvalerate) Co-Biopolymer Production from Rice Wastewater by Azohydromonas lata

 Background and objective: Biopolymers are environmental friendly, non-toxic renewable alternatives for conventional synthetic polymers. Rice wastewater contains high biochemical and chemical oxygen demands and organic contents mainly in form of starch which can cause serious environmental problems, while, it can be used as a potentially low-cost substrate for biopolymer production. The objective of the current study was to investigate the ability of Azohydromonas lata to produce poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (P3HB-co-P3HV) from rice wastewater in a batch system.Material and methods: Aspergillus niger was first used to hydrolyze the starch content of rice wastewater to fermentable soluble sugars. Then, the bacterium Azohydromonas lata was cultured in hydrolyzed wastewater at various C: N: P ratios to produce biopolymers. So, effects of different nitrogen and carbon sources on P (3HB) and P (3HV) contents at a C: N: P ratio of 100:4:1 were assessed.Results and conclusion: This study showed that Azohydromonas lata was able to produce poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (P3HB-co-P3HV) from rice wastewater in the presence of simple carbon sources and under limited nutrient conditions, especially phosphorus. The highest content of P (3HB) was achieved when ammonium sulphate was used as nitrogen source at a C: N: P ratio of 100:4:1. The highest recorded cell dry mass and biopolymer concentration were 4.64 and 2.8 g l-1 respectively, at a P(3HB) content in biomass of 60%  w w-1. Results indicated that phosphorus and nitrogen limitations could significantly affect P (3HB) production. In general, rice wastewater is a potential alternative for carbon sources such as glucose and maltose in polyhydroxybutyrate production.Conflict of interest: The authors declare no conflict of interest

Hydrogen as clean fuel via continuous fermentation by anaerobic photosynthetic bacteria, Rhodospirillum rubrum

Hydrogen has been considered a potential fuel for the future since it is carbon-free and oxidized to water as a combustion product. Bioconversion of synthesis gas to hydrogen was demonstrated in a continuous fermentation utilizing malate as a carbon source. Rhodospirillum rubrum, an anaerobic photosynthetic bacterium catalyzed water gas shift reaction which was used in this research. The synthesis gas (CO) was used as a source of energy along with tungsten light supplied for growth and bioconversion of the photosynthetic bacteria. The microbial process in fermentation media was carried out in continuous culture to observe the effect of light intensity, agitation and liquid dilution rate on hydrogen production. The maximum hydrogen yield at 500 rpm was 0.65 mmol H2/mmol CO. Desired media flow rate was preferable for high hydrogen production. At 0.65 ml/min media, hydrogen was produced at 7.2 mmol/h. This new approach, use of biocatalyst, can be considered as an alternative method to the conventional Fischer Tropsch synthetic reactions, which were able to convert synthesis gas into hydrogen. Key Words: Hydrogen, syngas, continuous bioreactor, Rhodospirillum rubrum, light intensity, agitation rate and flow rate. African Journal of Biotechnology Vol.3(10) 2004: 503-50

Biosorption of Cadmium(II) Ions by Saccharomyces cerevisiae Biomass from Aqueous Solutions

The biosorption of cadmium(II) ions onto Saccharomyces cerevisiae biomass from aqueous solutions was investigated. The cells were treated with 70% ethanol solution in order to increase the biosorption capacity of S. cerevisiae. The effect of solution pH, initial metal concentration and biomass dosage on biosorption by ethanol treated yeast was studied. Optima conditions of initial solution pH, Cd(II) ion concentration and biomass dosage were at 5, 37.5 mgL-1 and 0.1 gL-1, respectively. The Freundlich equation was applied to the experimental data. The maximum metal uptake value (qmax) was found as 25 mgg-1

Synthesis of Organic-Inorganic Hybrid Amine Based on Nanostructured Silicate Materials and Its Application for Removal of Heavy Metal Ions from Aqueous Solution

The heavy metals are nonbiodegradable that can accumulate in living tissues which cause cancers and neural problems in human. From an environmental health point of view, it is therefore necessary to remove them from aqueous solution and wastewater. In this research work, nanoporous silica SBA-15 was synthesized by hydrothermal method and then functionalized by three different concentrations of 3-aminopropyltriethoxysilane, namely 4 [(NH2(4mM)-SBA-15], 6 [NH2(6mM)-SBA-15] and 8 [NH2(8mM)-SBA-15] mM, in order to be used as adsorbent for lead, copper and cadmium ions removal. The materials have been characterized by means of X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), nitrogen adsorption-desorption, and FTIR spectroscopy. The results showed that the removal percentage was increased from 46.1 to 100 for lead, from 44.2 to 79.3 for copper and from 26.8 to 67.0 for cadmium with increasing concentration of amine groups from 4 to 8 mM. Thus, NH2(8mM)-SBA-15 was selected as an adsorbent in subsequent experiments. The effects of adsorbent dose, contact time, pH and initial concentration of metal ions on adsorption efficiency in batch system were studied. The experimental data were analyzed using the Langmuir and Freundlich isotherm models. Maximal equilibrium uptake capacity of 15.9 mg/g for lead, 13.1 mg/g for copper and 11.2 mg/g for cadmium was obtained. Consequently, the nano-structural adsorbent prepared has appropriate adsorption efficiency therefore it can be considered for the removal of heavy metal ions in future study

Application of Ozone and Granular Activated Carbon for Distillery Effluent Treatment

The main objective of this study was to investigate the treatment of distillery vinasse through the integrated process of ozone oxidation and Granular Activated Carbon (GAC) in a continuous process. The continuous process was carried out both by each of the GAC and ozone processes alone and by the combination of the two in order to investigate the synergistic effects of the two modes on COD and color removal in the treatment of vinasse from laboratory ethanol production from cane molasses. The continuous processes were performed at an ozone generation rate of 240mg/h, GAC dose of 100g, and at room temperature (25°C). Color removal efficiency of O3 was higher than its COD removal from vinasse. The COD and color removal efficiencies of the O3 process were about 25% and 74%, respectively. Moreover, GAC/O3 process was found to negatively affect the synergy of COD and color removal efficiency from distillery vinasse. This negative effect decreased by increasing influent pH level. The results indicate that the initial pH has a considerable effect on the three processes investigated

Desorption of Reactive Red 198 from activated carbon prepared from walnut shells: effects of temperature, sodium carbonate concentration and organic solvent dose

This study investigated the effect of temperature, different concentrations of sodium carbonate,and the dose of organic solvent on the desorption of Reactive Red 198 dye from dye-saturated activated carbon using batch and continuous systems. The results of the batch desorption test showed 60% acetone in water as the optimum amount. However, when the concentration of sodium carbonate was raised, the dye desorption percentage increased from 26% to 42% due to economic considerations; 15 mg/L of sodium carbonate was selected to continue the processof desorption. Increasing the desorption temperature can improve the dye desorption efficiency.According to the column test results, dye desorption concentration decreased gradually with the passing of time. The column test results showed that desorption efficiency and the percentage of dye adsorbed decreased; however, it seemed to stabilize after three repeated adsorption/desorption cycles. The repeated adsorption–desorption column tests (3 cycles) showed that the activated carbon which was prepared from walnut shell was a suitable and economical adsorbent for dye removal

Removal of Cd(II), Ni(II), and Pb(II) Ions in an Aqueous Solution by Chemically Modified Nanoporous MCM-41

MCM-41 includes a group of silica mesopore components with a high surface area whose adsorption capacities can be enhanced by modifying their surface with amine groups. In this study, the modified NH2-MCM-41 was used to investigate adsorption of Cd(II), Ni(II) and Pb(II) ions in a mixture of aqueous solutions. All the experiments were carried out in a batch system containing a solution of metal ions to study the effects of the initial metal concentration, adsorbent dosage, contact time, and solution pH. The results showed that optimum adsorption would be achieved at pH 5 and that adsorption capacity increased with increasing metal ion concentration but with decreasing adsorbent dosage. Experimental data were fitted with Langmauir and Freundlich models. Maximum adsorption capacities for Ni(II), Cd(II), and Pb(II) were 12.36, 18.25 and 57.74 mg/g, respectively. The results indicate that NH2-MCM-41 is an effective adsorbent for Ni(II), Cd(II) and Pb(II) ions with a high adsorption capacity

Efficiency of Immobilized Nano TiO2 on Fe-ZSM-5 Zeolite in Organic Pollutants Removal from Petroleum Refinery Wastewater

Effluents from oil refineries contain different concentrations of aliphatic and aromatic hydrocarbons. Given the toxicity of the aromatic fraction that is not readily degradable by conventional treatment processes, advanced processes are required for their removal. This study investigated the photocatalytic degradation and removal of organic contaminants from oil refinery effluents. For this purpose, TiO2-Fe-ZSM-5 photocatalyst was initially produced by immobilizing TiO2 into the structure of synthetic Fe-ZSM-5 zeolite. X-Ray diffraction, X-Ray fluorescence, Fourier transform infrared (FTIR) spectroscometry, scanning electron microscopy, transmission electron microscopy, and nitrogen sorption/desorption techniques were then employed to determine the structural and physicochemical properties of the products. High purity TiO2-Fe-ZSM-5 photocatalyst with a TiO2 percentage of 29.28 and a specific surface area of 304.6 m2g-1 was synthesized. The photocatalyst thus obtained was then applied for the removal of organic pollutants from the effluent of Bandar Abbas Oil Refinery. A maximum COD reduction of more than 80% was achieved under optimum conditions (i.e., pH: 4, catalyst concentration: 3 g/l, temperature: 45 °C, and UV exposure time: 240 min)

Determination of Optimal Temperature for Biosorption of Heavy Metal Mixture from Aqueous Solution by Pretreated Biomass of Aspergillus niger

Biosorption is a novel technology that uses dead and inactive biomass for removal of heavy metals from aqueous solution. Some parameters such as temperature, contact time, solution pH, initial metal concentration, biosorbent dose and also agitating speed of solution and biosorbent mixing can affect the amount of metal sorption by biosorbent. The aim of this study was to investigate the effects of different treatments of temperatures (25, 35, 45 and 55oC) on biosorption of metals mixture in order to determine optimal temperature for more metals removal from aqueous solution. This study uses dead and pretreated biomass of Aspergillus niger with 0.5N NaOH for removal of Zn(II), Co(II) and Cd(II). In all temperature treatments and in the case of all of heavy metals, maximum amount of metal sorption and concentration decrease was occurred in first 5 minutes and achieved to equilibrium after 20 minute. The percent of metals sorption show growth trend with temperature increase. Between 4 experimental treatments, 55oC treatment was shown maximum sorption and 25oC was shown minimum sorption amount. The percent of Cr(II) sorption was increase from 28.5% in 25oC to 44.7% in 55oC. Also, this increase was from 40% to 58% for Cd(II) and from 37.7% to 65.6% for Zn(II). About 60% of increase in sorption by A. niger was due to increase in temperature. Therefore the amount of metals sorption can be increase, only with temperature increase and without any biomass addition