Batch Experimental System Research Articles

Influence and mechanism of typical transition metal ions on the denitrification performance of heterotrophic nitrification-aerobic denitrification bacteria

To investigate the inhibitory effects of various transition metal ions on nitrogen removal and their underlying mechanisms, the single and combined effects of Cu2+ Ni2+ and Zn2+ on Heterotrophic nitrification-aerobic denitrification (HN-AD) bacteria Acinetobacter sp. TAC-1 were studied in a batch experiment system. The results revealed that increasing concentrations of Cu2+ and Ni2+ had a detrimental effect on the removal of ammonium nitrogen (NH4+-N) and total nitrogen (TN). Specifically, Cu2+ concentration of 10 mg/L, the TN degradation rate was 55.09%, compared to 77.60% in the control group. Cu2+ exhibited a pronounced inhibitory effect. In contrast, Zn2+ showed no apparent inhibitory effect on NH4+-N removal and even enhanced TN removal at lower concentrations. However, when the mixed ion concentration of Zn2++Ni2+ exceeded 5 mg/L, the removal rates of NH4+-N and TN were significantly reduced. Moreover, transition metal ions did not significantly impact the removal rates of chemical oxygen demand (COD). The inhibition model fitting results indicated that the inhibition sequence was Cu2+ > Zn2+ > Ni2+. Transcriptome analysis demonstrated that metal ions influence TAC-1 activity by modulating the expression of pivotal genes, including zinc ABC transporter substrate binding protein (znuA), ribosomal protein (rpsM), and chromosome replication initiation protein (dnaA) and DNA replication of TAC-1 under metal ion stress, leading to disruptions in transcription, translation, and cell membrane structure. Finally, a conceptual model was proposed by us to summarize the inhibition mechanism and possible response strategies of TAC-1 bacteria under metal ion stress, and to address the lack of understanding regarding the influence mechanism of TAC-1 on nitrogen removal in wastewater co-polluted by metal and ammonia nitrogen. The results provided practical guidance for the management of transition metal and ammonia nitrogen co-polluted water bodies, as well as the removal of high nitrogen.

Characterization and Optimization of Polymeric Bispicolamine Chelating Resin: Performance Evaluation via RSM Using Copper in Acid Liquors as a Model Substrate through Ion Exchange Method.

Advanced technologies of electronics industries have led to environmental contamination concerns, especially waste print circuit boards containing a very high concentration of copper (II) ions, which can be discharged in wastewater containing many contaminated metals. A low pH is a necessity for treating industrial wastewater containing heavy metals to meet engineering process design. A novel polymeric bispicolamine chelating resin, Dowex-M4195, was applied as an alternative for investigating the behavior of copper (II) in acidic solution via an ion exchange method in a batch experiment system. Characterization of physical and chemical properties before and after ion exchange were also explored through BET, SEM-EDX, FTIR and XRD. Response surface methodology was also applied for optimization of copper (II) removal capacity using design of experiment for selective chelating resin at a low pH. The results indicate that H+ Dowex-M4195 chelating resin had a high-carbon content and specific surface area of >64% and 26.5060 m2/g, respectively. It was predominantly macropore porous in nature due to the N2 gas adsorption isotherm and exhibited type IV with insignificant desorption hysteresis loop of H1-type. It was spherical and cylindrical. After the ion exchange process of copper (II)-loaded H+ Dowex-M4195, the specific surface area and total pore volume decreased by about 17.82% and 5.39%, respectively, as compared to H+ Dowex-M4195. Hysteresis loop, isotherm and pore size distribution were also similar. Regarding the functional group, the surface morphology and crystalline structures of H+ Dowex-M4195 showed copper (II) compound based on the structure of chelating resin that confirmed effective ion exchange behavior. The design of optimization indicated that copper (II) removal capacity of about 31.33 mg/g was achieved, which could be obtained at 6.96 h, pH of 2 (a desirable low pH), dose of 124.13 mg and concentration of 525.15 mg/L. The study indicated that the H+ Dowex-M4195 (which is commercially available on the market) can successfully be applied as an alternative precursor through the ion exchange method for further reuse and regeneration of the copper (II) in the electronic waste industries and other wastewater applications needed to respond the policy of biocircular green economy in Thailand.

Scenedesmus regularis: An alternative biosorbent for the efficient and fast removal of methylene blue

<p>This study focused on removing methylene blue (MB) from aqueous solutions using microalga Scenedesmus regularis as a biosorbent. The biomass was characterized by Fourier transform infrared spectroscopy (FT-IR) and field emission scanning electron microscopy (FE-SEM). The difference in thermal properties of the biomass was investigated by thermogravimetric analysis (TGA). The adsorption capacity of S. regularis was tested with different environmental key parameters (pH, temperature, biosorbent dosage, dye concentration, and contact time) in batch system experiments. The maximum adsorption capacity was 341.34 mg/g at a pH of 6.8, a temperature of 25 °C, a dye concentration of 250 mg/L, and a biosorbent concentration of 5 mg. Approximately 92% of the dye was removed within two minutes, and the removal efficiency reached 99% within 15 minutes. MB adsorption equilibrium data fit well with the Langmuir (R2=0.994) and Dubinin-Radushkevich (R2=0.993) isotherm models. The kinetic model of adsorption followed pseudo-second-order kinetics. Thermodynamic parameters showed that the adsorption process was endothermic and physical, favorable, and spontaneous. The results showed that S. regularis is an eco-friendly biosorbent with efficient performance that may be used for MB removal without any modification.</p>

The Effectiveness of <i>Scolymus Maculatus</i> in the Removal of Basic Blue Dye 41 in Aqueous Solutions: Kinetics and Thermodynamics

The presence of cationic dyes; especially the basic ones in an aqueous solution causes several problems. Therefore, it is necessary to reduce itfrom industrial effluents before being discharged into the environment. This study aimed to investigate the removal of Basic Blue 41 (BB41) dye from an aqueous solution using agricultural waste as an adsorbent. This study was conducted in a batch experimental system. The effect of various parameters such as initial dye concentration, pH, pH_zpc and adsorbent dosage was studied. The data were examined by Freundlich, Temkin, Debinin-Radushkevich, pseudo first order and pseudo second order kinetic, and thermodynamic parameters. The characterization of the adsorbent was determined by the Scanning Electron Microscopy (SEM), Fourier transform infrared (FTIR) and X-Ray Diffraction (DRX). The results of this work showed that the <i>Scolymus Maculatus</i> adsorbent was proven most effective in removing Basic Blue 41 from an aqueous solution at pH=7,09 with 85,14%. The results showed also that the adsorption process follows the Freundlich isotherm as well as pseudo-second-order kinetic. The results of the thermodynamic process showed that the adsorption is spontaneous and endothermic in nature.

Removal and Comparative Adsorption of Anionic Dye on Various MgAl synthetic Clay

In this study, the adsorption of Congo red dye in an aqueous solution on two synthetic clay adsorbents, MgAl-LDH (2:1) and MgAl-LDH (3:1), was investigated using batch system experiments. The adsorbents' characterization was carried out by various techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy FT-IR. The conditions applied in the adsorption experiments including the mass of adsorbent, initial concentration, contact time, pH, and temperature. The kinetic data were modeled by pseudo-first-order and pseudo-second-order. Langmuir and Freundlich's models analyzed the adsorption isotherms of Congo red on the two adsorbents. It was found that the adsorption process could be described by Langmuir isotherm. The maximum amount of adsorption is 285.71 and 166.66 mg/g for MgAl-LDH (2:1) and MgAl-LDH (3:1), respectively. Thermodynamic parameters such as enthalpy ∆H°, enthalpy ∆S°, and free enthalpy ∆G° were also evaluated to predict the nature of adsorption.

Purification of malachite green as a model biocidal agent from aqueous system by using a natural widespread coastal biowaste (Zostera marina)

The present paper aimed to perform an environmentally friendly and effective study on the purification of biocidal material using bioremediation technique, and in this context, a natural widespread coastal biowaste (Zostera marina) was applied to remove a model biocide from aqueous system. Herein, malachite green was selected as a common agent to evaluate the biosorption efficiency of waste biomaterial. The bioremediation properties of biosorbent were studied in a controlled batch experiment system by the optimization practice of operating parameters like biosorbent quantity, medium pH, time, pollutant concentration and temperature, and kinetic, thermodynamic, equilibrium, and characterization operations. The optimum operating conditions were considered as 10 mg, 4, 6 h, 15 mg L−1, and 25 °C, respectively. Elovich and Langmuir were found to be the best-fitted models, describing the experimental biosorption data. Thermodynamic study revealed a favorable nature of the cleanup process. The characterization analysis indicated the presence of various functional groups on the layered biosorbent surface involved on the pollutant treatment. The untreated biosorbent showed a good biocide purification performance with a value of 97.584 mg g−1, and it could thus be employed as an eco-friendly and cost-effective cleaning agent in environmental bioremediation studies.

Isotherm, kinetic and thermodynamic studies for the adsorption of methylene blue on almond leaf powder

In this study almond leaf powder (ALP) was used as an adsorbent for the methylene blue (MB) removal. The initial MB concentration, interaction time and temperature effects were investigated in a batch experimental system. The equilibrium data was modelled using Langmuir, Freundlich and Temkin adsorption isotherms, while kinetic parameters were determined using the pseudo first order (PFO), pseudo second order (PSO) and intra-particle diffusion (IPD) models. It was noted that the Freundlich model was the most convenient option compared to the Langmuir and Temkin models. The Freundlich model coefficients increased as the temperature increased, proving that adsorption process is favorable at higher temperatures. The results also indicated that the experimental and calculated qe values were close to each other, which shows that this process fits the PSO kinetic model with higher R2 values than other two models. Kinetic constants became closer to both temperatures and the initial concentrations and qe values increased with the increase in the concentration of MB. The initial MB concentration increased from 10 to 60 mg/L, while the adsorption capacity on ALP increased from 1.46 to 9.24 mg/g, 1.61 to 9.71 mg/g and 1.89 to 10.71 mg/g for 298, 308 and 323 K, respectively. Gibbs free energy, enthalpy and entropy of this separation process were determined as -1737.1 J/mol, 14.776 kJ/mol and 55.413 J/mol, respectively. Results of this study showed that ALP can be an alternative material for dye removal.

Absorption and Desorption Remediation of Environmental Pollution to Remove Heavy Metal Ions From Waste Water Using Batch experimental System

Graphite is the substance of allotropes of carbon forms with diamond, and amorphous carbon, Graphite considered one of methods that we can use it for adsorption of heavy metals ion from water, by a new sorbent material having functionalized for solid phase extraction (SPE) metals (Zinc and Cobalt) from aqueous solutions. Firstly we used Graphite substance by chemical process to convert it to Graphene and graphene oxide has been used in oxidation by hummer method process by using H2SO4 and KMnO4 that considered a good oxidizing materials. Graphene oxide is a Composite material fabricated from Graphite. Micrometer thick films of graphene oxide paper are also named as graphite oxide membranes, secondly we silanized it with 3-(trimethoxysilyl) propylamine to get (GO-Si) product, thirdly react this product with functional gropus (Aldehyde) (3,5,Di-tert-butyle-2-hydroxy-benzenaldehyde) to get (Go-Si-Ald) that form graphene Schiff base material, that we used it to several process under different laboratories factors such as (pH, different concentrations of metals / Zinc and Cobalt, different stirring time, with different temperatures), The adsorption of metals (Zn and Co) were investigated successfully, this is one of development method for treatment of waste and drinking water for reuse. This method is benefit to solve environmental problem which is harmful to health. All these work made by several instrumental analysis such as ICP, FTIR analysis, EDX, Uv-visible, TGA, TEM, SEM, XRD Analysis.

Effect of types of control materials in a modified sedimentation equipment batch laboratory scale

The purpose of this research is to be able to recognize laboratory scale sedimentation devices in the process of deposition through batch system experiments in a cylindrical tub, to explain how the relationship between time, height of deposition and concentration of various solids with sedimentation rates, can compare the precipitating materials used in the sedimentation process both manually and automatically, and can determine the performance of tools and sedimentation rates by using a variety of sedimentation and flocculant materials used in the sedimentation process both without the addition of flocculants or with the addition of flocculants. In supporting this research, the method used is experimentation and analysis. The sample is a mixture of media that is water - depositional material (solids) where the depositional material has previously been sieved and cleaned of impurities and the variables analyzed were deposition time, deposition height, suspension concentration and concentration of flocculant addition. the settling material used varies, among others: 50 grams, 100 grams, 150 grams, 200 grams, and 250 grams, then put into a settling tube. While the results can be obtained from visualization data that is based on more accurate observations and data processing conditions (measurements) obtained in the form of the influence of time on settling rate, the influence of sedimentation column height on settling rate and the effect of solid concentration on settling rate. From the results obtained from various settling materials, the settling speed for CaCO3 precipitates without flocculants and with flocculants is 4.43 cm / minute and 3.86 cm / minute. For the settling speed for tapioca flour depositor without flocculant and with flocculant is 23.64 cm / minute and 23.47 cm / minute. And for settling speed for dry soil sedimentation material without flocculant and with flocculant is 18.60 cm / minute and 15.10 cm / minute and for settling speed of active carbon precipitation material without flocculant and with flocculant is 7.76 cm / minute and 7 .05 cm / minute.

Biodegradation of reactive dyes by some bacteria using response surface methodology as an optimization technique

Water pollution as a result of contamination with dye-contaminating effluents is a severe issue for water reservoirs, which instigated the study of biodegradation of Reactive Red 195 and Reactive Blue dyes by E. coli and Bacillus sp. The effects of occupation time, solution pH, initial dyes concentrations, biomass loading, and temperature were investigated via batch-system experiments by using the Design of Experiment (DOE) for 2 levels and 5 factors response surface methodology (RSM). The operational conditions used for these factors were optimized using quadratic techniques by reducing the number of experiments. The results revealed that the two types of bacteria had a powerful effect on biodegradable dyes. The regression analysis revealed a good match of the experimental data to the second-order polynomial with a high coefficient of determination (R2). The optimum conditions achieved by E. coli were temperature (39.9 °C), initial concentration (99.6 mg L−1), biomass loading (14.9 VBiomass/VSolution), incubation time (1 day), pH (7.23), while the optimum conditions achieved by Bacillus sp. were temperature (28.3 °C), initial concentration (98 mg L−1), biomass loading (5.8 VBiomass/VSolution), incubation time (1 day), and pH (7.9) obtained from the desirability function.

Desorption Behavior of Fukushima-derived Radiocesium in Sand Collected from Yotsukura Beach in Fukushima Prefecture.

Beach sand samples were collected along a coastal area 32 km south of the Fukushima Daiichi Nuclear Power Plant (FDNPP) in Fukushima Prefecture, Japan, 5 years after the FDNPP accident. Desorption experiments were performed on the sand samples using seawater in a batch experimental system to understand the forms of existence of radiocesium in sand and their desorption behavior in a coastal environment. The percentage of radiocesium desorption decreased exponentially with an increase in the number of desorption experiments for the four sand samples, with 137Cs radioactivity from 16 to 1077 Bq kg-1 at surface and deeper layers from three sites. Total desorption percentage ranged from 19 to 58% in 12 desorption experiments. The results indicate that the weak adsorption varies with the sampling sites and their depth layer. To understand the desorption behavior of radiocesium in the sand samples, the desorption experiments were performed for a sand sample by using natural and artificial seawater, and NaCl solution in the presence and absence of KCl. The 137Cs desorption from the sand collected at a depth of 100 - 105 cm from the ground surface (137Cs radioactivity 1052 ± 25 Bq kg-1) was 0.1% by ultrapure water, 3.7% by 1/4 seawater and 7.1% by 1/2 seawater, 2.2% by 470 mM NaCl solution (corresponding to a similar concentration of seawater) and 10 - 12% by seawater, artificial seawater and 470 mM NaCl + 8 mM KCl solution. These results indicate that about 10% of radiocesium adsorbed on the sand is mainly desorbed by ion exchange of potassium ion in seawater, though the concentration of major cation, or sodium ion, in seawater makes a small contribution on 137Cs desorption from the sand samples.

Ciprofloxacin desorption from gel type ion exchange resin: Desorption modeling in batch system and fixed bed column

The aim of this paper was to assess the desorption of ciprofloxacin (CIP) from the Supergel™ SGC650H resin and to evaluate the possibility of future reuse of the adsorbent by applying adsorption cycles. Preliminary desorption tests by using different aqueous HCl concentrations as eluent agents and adsorption experiments with the previously treated resin with these same solutions were carried out in batch system to determine the best eluent condition. Physico-chemical characterization tests were performed for virgin and HCl-treated resin, evidencing changes on the resin’s structure and functional groups caused by the eluents. The preliminary results showed that the HCl concentration of 2 mol L−1 provided both the CIP-desorption efficiency from the resin and the improvement of CIP adsorption capacity. Therefore, this eluent concentration was applied for the further equilibrium experiments in batch system. Mathematical modeling was applied to the kinetic and equilibrium desorption data obtained in batch system, evidencing that internal diffusion model showed a good agreement with the experimental data. Based on the estimated parameters from the independent batch experiments, the model was able to adequately predict the desorption kinetic behavior in fixed bed column. Overall, the results showed that the HCl aqueous solution of 2 mol L−1 could be efficiently applied to assess adsorption cycles, due to the high desorption efficiency combined with the enhancement of the resin’s capacity. Furthermore, the present work provided a robust and predictive mathematical model, which could support the design and the scale up of industrial level equipment.

Optimization, isotherm and kinetics studies of azo dye adsorption on eggshell membrane

Eggshell membrane (ESM) was used as an adsorbent for adsorption of reactive red 195 (RR195) and reactive black 5 (RB5) dyes from aqueous solutions. The experimental conditions were optimized via batch system experiments for maximum azo dyes removal. Adsorption of the dyes was pH dependent highly, and the maximum adsorption of RR195 and RB5 occurred at pH 3.0 and 2.0, respectively. For both dyes, the adsorption process was seen to be obeyed pseudo-second order kinetic and the Langmuir isotherm models. Maximum adsorption capacities (Qmax) of ESM for RR195 dye and RB5 were found as 76.9 and 333.33 mg g-1, respectively. The thermodynamic parameters were calculated and the adsorption of the dyes was found to be as exothermic and spontaneous. Moreover, the structural characterization of the ESM was performed by FTIR and SEM analysis.

Redox transformation of soil minerals and arsenic in arsenic-contaminated soil under cycling redox conditions.

Changes in the saturation degree of aquifers control the geochemical reactions of redox-sensitive elements such as iron (Fe), sulfur (S), and arsenic (As). In this study, the effects of redox conditions and the presence of Fe and S on the behavior of As in a soil environment were investigated by observation in a batch experimental system. Arsenic was stable on Fe(III) solid surface in an oxidizing environment but was easily released into the aqueous phase following the reductive dissolution of Fe during an anoxic period. The alternating redox cycles led to a change in the concentrations of Fe, S, and As in both the aqueous and solid phases. The composition of Fe minerals changed to a less crystalline phase while that of solid phase As changed to a more reduced phase in both the As-contaminated natural soil and FeS-amended soil batch systems. This tendency was more prominent in the batch containing higher amounts of total Fe and S. These results show that a redox cycle can increase the possibility of As contamination of groundwater during dissolution and reprecipitation of Fe minerals and simultaneous microbial reduction of S and/or As species.

Adsorptive Removal of Basic Yellow Dye Using Bigadiç Zeolites: FTIR Analysis, Kinetics, and Isotherms Modeling

The adsorptive removal efficiency of Basic Yellow Dye (Astrazon Yellow 7GLL) from aqueous solutions was studied using different types of modified zeolites in an agitated single‐stage batch experimental system. Zeolite samples consisted of mainly clinoptilolite, collected from Bigadic Region of Turkey. The optimum adsorbent amount was found as 0.5 g in the primary experiments. Then, the adsorption kinetics with a constant initial dye concentration of 50 mg/L, agitation speed of 250 rpm, and temperature of 25°C for a period of 180 min were investigated. Three kinetic models namely, pseudo‐first‐order, pseudo‐second‐order non‐linear kinetic models, and the intra‐particle diffusion were used to describe the kinetic data of adsorption process. Non‐linear fittings of the Langmuir and Freundlich adsorption isotherm models were applied to the experimental equilibrium data obtained with dye concentrations in the range of 12–550 mg/L. The adsorption capacities (Qo) of zeolite samples for basic dye were in the range of 17.8–21.2 mg/g. Different analytical methods were used to investigate the influence of the different treatments on the zeolite surface and understanding of the adsorptive removal of dye using natural and modified zeolites. It was concluded that the spectroscopic results agree with the results obtained by kinetic and adsorption experiments as the acidic pre‐treatment zeolite has the highest removal rate for dye molecules since the concentration of various active sites (oxygen species, free Al+, and Si+ sides, etc.) to increase on the surface. On the contrary, basic treatment causes the loading of the surfaces with hydroxyl groups and these interact with each other via H‐bond and causes increased removal rate. © 2018 American Institute of Chemical Engineers Environ Prog, 38: S185–S195, 2019

Parameter optimization for Cr(VI) adsorption breakdown curves onto cocoa shell

The aim of the present investigation was to evaluate the cocoa shell (Theobroma cacao L .) for its use in the adsorption of hexavalent chromium in aqueous solution using packed bed column, applying the surface response method (SRM) in order to determine the optimum values of the variables involved in the process. The adsorption tests were carried out with these values. Was used a central composite experiment design with star points. The biomass was washed, dried, decreased size and sieved; the experiments were carried out at 25°C, at different particle sizes, flow rate and amount of biomass, in columns in continuous system; obtaining a percentage of removal of 39 .16% of C (VI) . Was obtained when performing the experiments in batch system that at a size of 0 .355mm particle favors the adsorption . From the adsorption tests in the column using the optimum parameters obtained by the MSR, was obtained a removal percentage of 62 .65%; finding that the models of Yoon-Nelson and Thomas were those that adjusted the experimental data of the rupture curve, with R2 = 0 .98. It’s concluded that the cocoa shell is a good precursor of bioadsorbents and that the most influential variables in Cr (VI) adsorption in batch and continuous systems are particle size and bed height.

Removal of Iron and Manganese from Natural Groundwater by Continuous Reactor Using Activated and Natural Mordenite Mineral Adsorption

Mordenite minerals derived from Sukabumi natural green stone founded in Indonesia was tested in order to remove iron and manganese from natural groundwater. This research used two types of adsorbents which were consisted of physically activated and natural mordenite. Physical activation of the mordenite was carried out by heating at 400-600°C for two hours. Batch system experiments was also conducted as a preliminary experiment. Batch system proved that both activated and natural mordenite minerals were capable of reducing iron and manganese concentration from natural groundwater. Then, continuous experiment was conducted using down-flow system with 45 ml/minute of constant flow rate. The iron & manganese removal efficiency using continuous reactor for physically activated and natural mordenite were 1.38–1.99%/minute & 0.8–1.49%/minute and 2.26%/minute & 1.37-2.26%/minute respectively. In addition, the regeneration treatment using NH4Cl solution managed to improve the removal efficiency of iron & manganese to 1.98%/minute & 1.77-1.90%/minute and 2.25%/minute & 2.02–2.21%/minute on physically activated mordenite and natural mordenite respectively. Subsequently, the activation of the new mordenite was carried out by immersing mordenite in NH4Cl solution. This chemical activation showed 2.42-2.75%/minute & 0.96 – 2.67 %/minute and 2.66 – 2.78 %/minute & 1.34 – 2.32 %/minute of iron & manganese removal efficiency per detention time for chemically activated and natural mordenite respectively.

Adsorption of uranium from uranium mine contaminated water using phosphate rock apatite (PRA): Isotherm, kinetic and characterization studies

Adsorption of uranium (U) from real mine contaminated water (U 1.652mg/L) by phosphate rock apatite (PRA) was investigated in the batch experiment and flow column test system. In batch experiment, the equilibrium adsorption amount is 0.1133mg/g with the highest uranium removal efficiency of 76.89% under the ratio of solid to liquid (1:100) in 15h. And the pH of wastewater became neutral (pH 7.51) from acidic (pH 3.88) after adsorption equilibrium. The saturated adsorption amount (0.2021mg/g) in batch experiment is higher than the maximum accumulative adsorption amount (0.0684mg/g) in column experiment. Langmuir model and pseudo-second order kinetic model are fitted well and, indicating that PRA is a favorable adsorbent with monolayer coverage and a chemisorption for uranium. Moreover, the surface morphology of the adsorbent by SEM confirmed the surface changes after uranium adsorption. XRD spectra showed that two new mineral phase of Metaankoleite [K(UO2)(PO4)·3H2O], Chernikovite [H2(UO2)2(PO4)2·8H2O] have been generated on PRA after uranium adsorption, but which were trace for relatively low uranium concentration in tested polluted water. In addition, the FT-IR spectra results confirmed the uranium in contaminated water was adsorbed onto the PRA in the form of (O=U=O)2+ with the participation of the PO43–in binding of it.

Production of docosahexaenoic acid by Aurantiochytrium sp. ATCC PRA-276.

The high costs and environmental concerns associated with using marine resources as sources of oils rich in polyunsaturated fatty acids have prompted searches for alternative sources of such oils. Some microorganisms, among them members of the genus Aurantiochytrium, can synthesize large amounts of these biocompounds. However, various parameters that affect the polyunsaturated fatty acids production of these organisms, such as the carbon and nitrogen sources supplied during their cultivation, require further elucidation. The objective of this investigation was to study the effect of different concentrations of carbon and total nitrogen on the production of polyunsaturated fatty acids, particularly docosahexaenoic acid, by Aurantiochytrium sp. ATCC PRA-276. We performed batch system experiments using an initial glucose concentration of 30 g/L and three different concentrations of total nitrogen, including 3.0, 0.44, and 0.22 g/L, and fed-batch system experiments in which 0.14 g/L of glucose and 0.0014 g/L of total nitrogen were supplied hourly. To assess the effects of these different treatments, we determined the biomass, glucose, total nitrogen and polyunsaturated fatty acids concentration. The maximum cell concentration (23.9 g/L) was obtained after 96 h of cultivation in the batch system using initial concentrations of 0.22 g/L total nitrogen and 30 g/L glucose. Under these conditions, we observed the highest level of polyunsaturated fatty acids production (3.6 g/L), with docosahexaenoic acid and docosapentaenoic acid ω6 concentrations reaching 2.54 and 0.80 g/L, respectively.

Investigation of equilibrium, kinetics and thermodynamics of extracted chitin from shrimp shell in reactive blue 29 (RB-29) removal from aqueous solutions

The presence of reactive dyes in aqueous medium cause many problems; therefore, it is necessary to reduce its content in industrial effluents before their discharge into environment. The aim of this study was to investigate the removal of reactive blue 29 (RB-29) dye from aqueous solutions using extracted chitin from shrimp shells as an adsorbent. This study was conducted in a batch experimental system. After extraction of chitin from shrimp shells, the effects of different variables such as pH, RB-29 concentration, contact time and adsorbent dose were investigated. Furthermore, adsorption isotherms, thermodynamics and kinetics of the process were also studied. The results of this study showed that the maximum adsorption capacity (q(max)) of chitin was 116.07 mg/g at a RB-29 concentration of 50 mg/L and contact time of 90 min. In addition, the maximum adsorption was observed at pH = 3 and adsorbent dosage of 0.2 g/L. The experimental data showed that the results were consistent with the Langmuir isotherm model. According to the results of thermodynamic study, standard entropy change Delta S is equal to 25.40 J/mol K, standard enthalpy change Delta H is equal to 7,054.39 J/mol and standard Gibbs free energy values (Delta G) were negative, that represents a spontaneous and endothermic process of RB-29 adsorption by the extracted chitin. Moreover, adsorption kinetics followed the pseudo-second-order kinetic model. Based on the results of this study it can be concluded that chitin can efficiently remove RB-29 dye from aqueous solutions. Keywords Author Keywords:Reactive blue 29; Chitin; Adsorption; Isotherms; Thermodynamics; Kinetics