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In this study, the microalga Chlorococum humicula was evaluated as a potential source of carotenoids and chlorophylls, and extraction of these pigments with liquefied dimethyl ether (DME) as an alternative green solvent was investigated. Carotenoids and chlorophylls in the algae were identified by spectral and comparative band ratio analyses. The liquefied DME extraction was shown to be a rather fast process for the extraction of pigments from C. humicula at relatively high yields. The effects of the extraction solvent: sample ratio, time, and temperature in the liquefied DME extraction of C. humicola on the yields of neoxanthin, violaxanthin, lutein, chlorophyll-b, chlorophyll-a, as well as the total carotenoids and chlorophylls, were determined. The highest total carotenoids yield (4.14 mg/g dry weight algae) and total chlorophylls yield (8.45 mg/g dry weight algae) were obtained using a 45:1 (w/w) liquefied DME: algae wet weight ratio for 20 min at 41 °C. At this condition, extraction of 91 % and 35 % of the total carotenoids and chlorophylls, respectively, was attained. In contrast, the extraction yield and percentage recovery of carotenoids obtained with acetone, a conventional solvent, was found to be lower than that of the liquefied DME, suggesting that liquefied DME has a higher selectivity for the less polar carotenoids than that of acetone.

Photoautotrophic cultivation of Chlorococcum humicola was performed in batch and continuous modes in different cultivating system arrangements to compare biomass and carotenoids' concentration and their productivities. Batch result from stirred tank and airlift photobioreactors indicated the positive effect of increasing light intensity on growth and carotenoid production, whereas the finding from continuous cultivation indicated that carotenoid enhancement preferred high light intensity and nitrogen-deficient environment. The highest biomass (1.31 ± 0.04 g L-1) and carotenoid (4.59 ± 0.06 mg L-1) concentration as well as the highest productivities, 0.46 g L-1 d-1 for biomass and 1.61 mg L-1 d-1 for carotenoids, were obtained when maintaining high light intensity of 10 klx, BG-11 medium and 2% (v/v) CO2 simultaneously, while the highest carotenoid content (4.84 mg g-1) was associated with high light intensity and nitrogen-deficient environment, which was induced by feed-modified BG-11 growth medium containing nitrate 20 folds lower than the original medium. Finally, the cultivating system arranged into smaller stirred tank photobioreactors in series yielded approximately 2.5 folds increase in both biomass and carotenoid productivities relative to using single airlift photobioreactor with equivalent working volume and similar operating condition.

The tie-line and solubility data, i.e. formic acid (FA) + n-butanol + water + NaCl, were resolved at T = 298.15 K and under ambient pressure. The Othmer–Tobias equation was applied in this study. T...

The solubility data of the salt of 2-mercaptobenzothiazole with cyclohexylamine (2-MBT-CHA) and tert-butylamine (2-MBT-TBA) in solid-liquid equilibrium, in various alternative solvents, are indispensable for a preliminary industrial application aimed at producing sustainable and renewable materials. In this paper, the solubility behavior of 2-MBT-CHA and 2-MBT-TBA, in various solvents (1,4-dioxane, methyl isobutyl ketone (MIBK), toluene and water) at low temperatures ranging from 303.15 to 348.15 K, has been studied. From the experimental data, it was found that the solubility of 2-MBT-CHA and 2-MBT-TBA increased when temperature increased. In addition, it was found that surface tension and polarity index were strongly dependent on the solubility of 2-MBT-CHA and 2-MBT-TBA. The solubility of 2-MBT-CHA and 2-MBT-TBA is in the following sequence, MIBK,4-Dioxane, toluene and water. To conclude the experimental data, thermodynamic models such as the polynomial empirical, the Van't Hoff, modified Apelblat, the semi-empirical Buchowski–Ksiazczak, the Wilson and the UNIQUAC were investigated. The Wilson model proved to be the most suitable for predicting the solubility behavior of 2-MBT-CHA and 2-MBT-TBA with temperature. Thermodynamic parameters were also investigated. Hence, it was noted that the dissolution process of 2-MBT-CHA and 2-MBT-TBA in investigated solvents is endothermic and spontaneous. The solubility of 2-MBT-CHA and 2-MBT-TBA obtained in solvents in this experiment will provide essential support for 2-MBT-CHA and 2-MBT-TBA industrial design and further theoretical studies.

During the cultivation of Chlorococcum humicola in airlift photobioreactors, significant wall-growth biofilm was observed, leading to severe light limitation and decreased biomass production. Experiments were conducted, therefore, to assess the possibility of using plastic media to reduce algal wall-growth on the inside surface of photobioreactors. As a result, lab-scale internal-loop airlift photobioreactors were built and operated using different commercial plastic media (MB5 and beads) and aeration rates (0.6 to 1.0 vvm). Without plastic media, significant wall-growth biofilm was observed on the draft tube and the lower section of photobioreactors. It was noted that when MB5 and beads at 5% and 10% by volume of photobioreactor were used, significantly lower biofilm attachment was seen on the surface and biomass concentration in bulk liquid increased 25% as compared to that without plastic media. The separation of plastic media from algal biomass and liquid was easy due to the specific gravity of the media slightly less than that of water.

The tie-line and solubility data for the systems containing formic acid (FA), water, and methyl isobutyl ketone (MIBK) + NaCl were determined experimentally at temperature 298.15 K and atmospheric pressure. The effect of salt 0.05–0.15 mass fraction (base on mass of initial water) was investigated. Binary interaction parameters were ascertained by comparing the experimental tie-line data with the nonrandom two-liquid model (NRTL) correlations. The tie-line data of the systems were analyzed using the Othmer–Tobias, Hand, and Bachman correlation equations. Separation factors and distribution coefficients were assessed. The results show that enlargement of the two–-hase region occurred when the concentration of salt increased in the initial aqueous phase; adding salt to the system proved beneficial in separating FA from water.

Amoxicillin extraction was conducted using the single organic extractant namely trialkylmethylammonium chloride (Aliquat 336), di-(2-ethylhexyl)-phosphoric acid (D2EHPA) and tributylphosphate (TBP) and followed by the synergistic extraction using the binary mixtures of the mentioned extractants. Maintaining an initial pH of amoxicillin aqueous solution at 10 yielded the highest extraction percentage for all extractants. Increasing extractant concentrations from 2 to 12 mM produced the positive effect on amoxicillin separation for all extractants except for TBP with the highest extraction percentage and distribution coefficient reported at 86.2 ± 1.10% and 6.25 ± 0.267, respectively when maintaining Aliquat 336 at 12 mM. Synergistic extraction was observed when the mixtures of D2EHPA and TBP as well as Aliquat 336 and TBP were employed with the maximum extraction percentage and distribution coefficient reported at 90.4 ± 0.39% and 9.44 ± 0.459, respectively when maintaining the molar ratio of Aliquat 336 to TBP at 10:2.

A large amount of industrial waste containing precious metals (PMs) has become a significant issue for the recovery of PMs. The success of PM extractions via hydrometallurgical processes using various types of ionic liquid (IL) extractants has been widely reported. An understanding of their extraction mechanisms and influencing factors is advantageous for further development and design, especially future utilization in industries. This review focuses on the extraction mechanisms of PMs using ILs as extractants in the liquid-liquid extraction or solvent extraction process. Factors influencing their extraction mechanisms and efficiency are described. Different types of ILs used in the extractions of gold (Au(III)), silver (Ag(I)), palladium (Pd(II)) and platinum (Pt(IV)) have been promoted. Moreover, the correlation of calculating parameters with the PM extractions is presented. Finally, their future aspects are recommended.

The separation of Nd(III) via hollow fiber supported liquid membrane (HFSLM) and mass transfer analysis was studied. At pH of 4.5, 0.5 M DNPPA as extractant, 3 M H2SO4 as stripping solution, flow rates of feed and stripping solutions of 100 mL/min and temperature of feed and stripping solutions of 313 K. Optimum extraction and stripping reached 98% and 95%. The mass transfer due to chemical reaction is the mass transfer—controlling step. The experiment data fitted in well with the mass transfer model. The average deviation in the feed side was below 2%.

The influence of temperature on the separation of amoxicillin via HFSLM containing the carrier Aliquat 336 was systematically investigated. Mass-transfer parameters including distribution ratio and flux as well as thermodynamic properties namely ΔH and ΔG were also determined at different temperatures ranging from 278.15 K to 318.15 K. The positive value of the enthalpy change (24.5778 kJ/mol) indicated that the extraction process is endothermic reaction. Further, the positive value of the entropy change (112.0145 J/mol K) and the negative value of the Gibbs free-energy indicated that the extraction process is forward reaction. It was found that by increasing the temperature of the system from 278.15 to 318.15 K, extraction of amoxicillin increased from 81.81% to 89.65% and the stripping of amoxicillin increased from 76.63% to 84.70% respectively. Activation energy (Ea) of amoxicillin extraction was found to be 44.28 kJ/mol. This implied that the chemical reaction was the mass transfer controlling step. The mass transfer coefficients in the membrane phase were found to be less than the mass transfer coefficients in the feed phase within the range of temperatures i.e. 278.15–318.15 K. This implied that the mass transfer process in the membrane phase was the rate controlling step.

This study evaluated the performance of land-based compact aquaculture system integrating fibrous nitrifying biofilters and solid removal unit. The first experiment indicated that the compact aquaculture system with total biofilter length of 6.0 m and single solid separating was able to accommodate aquaculture weight as high as 5.0 kg/m3, which corresponded to nitrogen loading rates of 8.4 mg N/L/day. In the second experiment, more effective solid-liquid separation and good water quality were achieved when solid separating unit was replaced by filtration unit with Japanese mats as filtered media, and cleaning of biofilters and filtration unit was conducted in every 4 days. Next, the compact aquaculture system was employed to cultivate tilapia without water-exchange for 60 days using the described strategies. TAN and nitrite were well below acceptable limit of 1.0 mg N/L; suspended solids varied between 20 and 35 mg SS/L; and harvesting fish weights were 10.4 kg/m3. Fish survival rate at 97% and average growth rate of 3.45 g/day were reported. Finally, solid removal remained the critical factor for successful aquacultures in the compact system even under extensive or semi-intensive aquaculture cultivation, and finally nitrogen mass balance indicated that nitrification-denitrification were main treatment pathways while solid removal only prolonged the activity of nitrifying biofilters.

The separation experiments of amoxicillin via hollow fiber supported liquid membrane (HFSLM) were performed under various operating conditions to find the optimal parameters i.e. pH, feed concentration, carrier concentration, and flow rates of feed and stripping solution. Percentages of extraction and recovery of amoxicillin from the feed phase reached 85.21% and 80.34%, respectively. The aqueous-phase mass transfer coefficient ( k f ) and organic-phase mass transfer coefficient ( k m ) were reported to be 3.57 × 10 −2 and 0.70 × 10 −2 cm/s, respectively. Furthermore, a mathematical model was developed to predict the concentration of amoxicillin at different times. The results showed promising agreement with experimental data.

Purification of Sn(IV) and recovery of Pd(II) from flexible printed circuit board (FPCB) industry wastewater via HFSLM has been presented. This work examined the influence of extractant concentration in the liquid membrane, HCl concentration, and flow rates of feed and stripping solutions. The thermodynamic properties were also investigated. The results showed that percentage of recovery of Pd(II) was 100% and purify 84% of Sn(IV) remaining in the feed solution. The Sn(IV) and Pd(II) kinetic reaction orders approached 1.0 and the reaction rate constants were read at 0.00301 and 0.08509 min −1 , respectively. The experimental results were agreed with the mathematical model.

Cultivation of recently identified Gluconobacter nephelii to produce 1,3-dihydroxyacetone (DHA) was conducted using the growth medium containing the external nitrogen source from agro-industrial wastes. Cell cultivation in 250 mL glass flasks using 80 g/L glycerol and corn steep liquor as nitrogen source yielded the highest biomass (1.75 ± 0.23 g/L) and DHA (49.5 ± 3.14 g/L) concentrations as compared to other nitrogen sources (i.e., glutamic mother liquor and soybean meal hydrolysate). Subsequent cultivation in larger bioreactors (32 L) with corn steep liquor as the preferred nitrogen source indicated that internal-loop airlift bioreactor yielded significantly higher biomass and DHA concentrations than flat-panel airlift and bubble column bioreactors. Further optimization of internal-loop airlift photobioreactor revealed that DHA production in G. nephelii depended on the aeration rates, with the maximum DHA concentrations (46.09 ± 1.01 g/L) obtained when maintaining the aeration rates at 0.64 vvm.

The separation of Nd(III) from lanthanide series via hollow fiber supported liquid membrane (HFSLM) using synergistic extractant was investigated. Optimum extraction and stripping obtained were 94.5% and 85.1% using D2EHPA and TOPO mixtures (0.5:0.5 M/M) as the synergistic extractant. Reaction order for both extraction and stripping were first-order with rate constants of 1.444 and 1.338 min−1, respectively. The experimental results were used to correlate with the models. Results showed that the concentration of Nd(III) from the experiment fitted in well with the model results. The average deviation was 1.95% and 2.18% for predictions in both feed and stripping sides, respectively.

The separation of Nd(III) from mixed rare earths via hollow fiber supported liquid membrane (HFSLM) was examined. Percentages of extraction and stripping of Nd(III) attained were 95% and 87%, respectively. Optimum condition was achieved using 4.5 pH of feed solution, 0.5 M 2-ethylhexyl-2-ethylhexyl phosphoric acid (HEHEPA) dissolved in octane as the extractant and 4 M HNO3 of stripping solution. The flow rates of both feed and stripping phase were 100 mL/min. The mathematical model was developed on the conservation of mass which consisted of convection, diffusion, reaction and accumulation. The model results prediction proved to be in good agreement with the experimental data at an average standard deviation of 1.9% and 1.2%, respectively.

The biphasic recognition chiral extraction process was developed and applied to separate amlodipine enantiomer. The chiral extraction system contained tartaric acid derivatives in the organic phase and β-cyclodextrin derivatives in the aqueous phase. The effect of extraction equilibrium time and the influence of different types of tartaric acids, types of β-cyclodextrin derivatives, organic solvents, and buffer pH were investigated. The results indicated that hydroxypropyl-β-cyclodextrin (HP-β-CD) showed a higher recognition ability toward (S)-amlodipine than (R)-amlodipine while dibenzoyl-D-tartrate demonstrated the strongest ability among tartaric acid derivatives to bind with (R)-amlodipine. The distribution ratios for (S)-amlodipine (kS) and (R)-amlodipine (kR) gave optimum values at pH 5.0 of 16.54 and 0.78, respectively. Biphasic chiral recognition extraction has great significance for preparative separation of (S)-amlodipine. It can also be used to design and apply the enantioseparation process.

This study intended to evaluate the performance of land-based aquaculture system integrating solids separating units, nitrifying biofilters, and tubular denitrifying reactor during the closed-water tilapia cultivation for 98 days. Operation of both solids separating units was able to maintain suspended solids (SS) concentrations in the rearing tank below 35 mg SS/L. Simultaneous operation of nitrifying biofilters, ORP-controlled denitrifying reactor, and two solids separating units was capable of maintaining total ammonia nitrogen (TAN) and nitrite concentrations substantially below 1.0 mg N/L and nitrate concentrations less than 12.0 mg N/L despite nitrogen loading rate and tilapia weight density were as high as 21.6 mg N/L/day and 17.2 kg/m 3 , respectively. Without solids separating units, TAN and nitrite concentrations drastically increased above the acceptable limits of 1.0 mg N/L. Finally, the result of nitrogen balance analysis indicated that nitrification and denitrification were the primary treatment pathways in this recirculating system capable of removing 49.8% of total nitrogen input, whereas solids separating units removed 9.5% of total nitrogen input yet their presence was essential for sustaining the activity of nitrifying biofilters for an extended period.

Continuous production of diatom Entomonies sp. was performed in mechanically stirred tank and flat-panel airlift photobioreactors (FPAP). The maximum specific growth rate of diatom from the batch experiment was 0.98 d(-1). A series of dilution rate and macronutrient concentration adjustments were performed in a stirred tank photobioreactor and found that the dilution rate ranged from 0.7 to 0.8 d(-1) and modified F/2 growth media containing nitrate at 3.09 mg N/L, phosphate at 2.24 mg P/L, and silicate at 11.91 mg Si/L yielded the maximum cell number density. Finally, the continuous cultivation of Entomonies sp. was conducted in FPAP using the optimal conditions determined earlier, resulting in the maximum cell number density of 19.69 × 10(4) cells/mL, which was approximately 47 and 73% increase from the result using the stirred tank photobioreactor fed with modified and standard F/2 growth media, respectively.

The daily addition of tilapia feed and tapioca starch at the C : N weight ratio of 16:1 was conducted to examine the effectiveness of biofloc-mediated assimilation and nitrification in the zero-water exchange tilapia cultivation tanks. Inorganic nitrogen concentrations in treatment tanks receiving feed and tapioca starch indicated profiles, which resembled the start-up of biofilters. Assimilation was essential for the control of inorganic nitrogen concentrations prior to the occurrence of complete nitrification as confirmed by an increase in suspended solids concentration from 52 to 1180 mg SS/L, a slower rate of total ammonia nitrogen (TAN) and nitrite accumulation, and lower concentrations of TAN and nitrite relative to those in control tanks receiving only feed addition. Effective control of inorganic nitrogen concentrations (i.e., TAN and NO2-N

The upflow bioreactor system without biomass-liquid separation unit was evaluated for its efficacy in sustaining autotrophic nitrification and denitrification (AND). The bioreactor system was capable of sustaining AND by means of carefully controlled oxygenation to achieve the maximum NH(4)(+)-N removal rate of 0.054 g N gVSS(-1) day(-1) (38% removal efficiency) at the oxygen influx and nitrogen loading rate of 3.68 mg O(2) h(-1) L-bioreactor(-1) and 182 mg N day(-1) L-bioreactor(-1), respectively. Additional nitrogen removal was achieved in a two-stage bioreactor configuration due to endogenous denitrification under long mean cell residence time. Quiescent conditions maintained in the bioreactor provided stable hydrodynamic environments for the chemoautotrophic biomass matrix, which revealed porous, loosely-structured, and mat-like architecture. More than 95% of the total biomass holdup (1.3-1.5 g VSS) was retained, thereby producing low biomass washout rate ( approximately 40 mg VSS day(-1)) with VSS < 11 mg VSSL(-1) in the effluent.

This work examined the feasibility of applying shrimp diets to establish nitrification on submerged fibrous biofilters. It also investigated the performance of a proposed zero-water exchanged aquaculture system, which integrated growing of aquatic stocks and operation of acclimated biofilters in the same environment. Addition of shrimp diets fully established nitrification within 3 weeks as indicated by continuous increase of nitrate and trivial levels of ammonium and nitrite. A series of batch experiment revealed an average ammonium degradation rate of 24.1mg Nm(-2) day(-1). Zero-water discharged tilapia cultivation could be carried out in the proposed aquaculture system for at least 44 days when daily inorganic loadings increased from 1.24 to 10.78mg Nl(-1) day(-1). The corresponding daily growth rates of tilapia from the proposed aquaculture systems integrated with acclimated biofilters varied from 3.01 to 3.35g day(-1), which was approximately 7-16% better than numbers from the systems using non-acclimated biofilters.