Effect Of Initial Phosphate Concentration Research Articles

Astaxanthin accumulation in the green microalga Haematococcus pluvialis: Effect of initial phosphate concentration and stepwise/continuous light stress

Nutrient composition and light stress significantly affect the productivity of astaxanthin in Haemotococcus pluvialis. Hence, the present study aimed to investigate the effect of initial phosphate concentration and two distinct light regimes on astaxanthin accumulation in H. pluvialis.In the green stage, microalgae were cultivated in different initial phosphate concentrations under 2000 lx and a 12:12 h photoperiod. To initiate astaxanthin accumulation, an increased light intensity of 5000 lx was provided using two methods; (i) stepwise light stress, where a 12:12 h photoperiod was provided for 14 days, followed by 14 days of continuous illumination, and (ii) continuous illumination for 28 days.Phosphate limitation and continuous light stress were favourable to enhance cellular astaxanthin accumulation, which reached 7% by weight. The highest astaxanthin concentration of 27.0 ± 1.9 mg/L and lowest specific light energy consumption of 32.9 ± 2.3 kW h/g astaxanthin were reported in cultures grown in 41 mg/L phosphate under continuous light stress.

Recyclable adsorbents based on Fe3O4 nanoparticles on lanthanum-modified montmorillonite for the efficient phosphate removal.

Montmorillonite (MMT) clay modified with lanthanum (La) ions and Fe3O4 nanoparticles was proposed for the effective removal of phosphate ions from aqueous solution. Characterisation of the adsorbent using FTIR, SEM, XRD, XPS, XRF, BET and VSM techniques were carried out. The effects of initial phosphate concentration, contact time, dosage and pH on the phosphorus adsorption were investigated. La-MMT/Fe3O4 exhibited an excellent adsorption capacity of up to 14.35 mg/g, with 97.8% removal within 60 min. Langmuir isotherm model fits well with the equilibrium isotherm data, with a maximum adsorption capacity of 15.53 mg/g at room temperature. The kinetic study was well fitted with pseudo-second-order kinetics, and the adsorption rate was mainly controlled by liquid-film diffusion. The manufactured adsorbent was effectively regenerated using 0.1 M NaOH solutions, with 90.18% adsorption efficiency remaining after six adsorption/desorption cycles. These results demonstrate that La-MMT/Fe3O4 provides an example of regenerable high-performance adsorbents for removal of PO43- from wastewater.

Enhanced Removal of Phosphates by the Adsorbent Consisting of Iron Oxide Loaded on Porous Chitosan/Cellulose Acetate Particle

The effective and economical removal of phosphates from aqueous solution, mostly applied in waste water treatment, is one of the significant issues globally. Removal of phosphates ions in aqueous solution was analysed by chitosan blended with cellulose acetate, and iron oxide loaded chitosan-cellulose acetate adsorbents. The adsorbents were made in the form of beads. Batch experiments were performed to investigate the performance of the beads under various conditions on phosphate adsorption. Contact time, effect of initial phosphate concentration, adsorbent dosage, pH and temperature were investigated. Zeta potential measurements were also undertaken. The results showed that the adsorption process was highly pH dependent. The adsorption kinetics data were modelled with the application of adsorption reaction models and adsorption diffusion models. The results revealed that the pseudo 2nd order model was the best fitting in all cases. The experimental data were tested with Langmuir and Freundlich isotherms. The equilibrium data were well fitted to the Langmuir isotherm model with a maximum adsorption capacity of 958 μg/g. The Freundlich isotherm model also had a close fit with a maximum adsorption of 233 μg/g, which was very close to the experimental maximum adsorption. The mechanism of adsorption followed two stages in which the first one was fast followed by a slower gradual stage. SEM images showed that the adsorbent was macroporous. Fourier Transform Infrared Red (FT-IR) Spectroscopy, X-ray Diffraction Spectroscopy (XRD) and X-ray photoelectron Spectroscopy (XPS) showed that the phosphate adsorption on the HFO-CS/CA beads was due to surface complexes, and mainly involved Nitrogen atoms. HFO loading also increased surface area.

Kinetic and thermodynamic evaluation of phosphate ions binding onto sevelamer hydrochloride

Sevelamer hydrochloride is the first non-aluminium, non-calcium-based phosphate binder developed for the management of hyperphosphatemia in end stage renal diseases. It is a synthetic ion-exchange polymer which binds and removes phosphate ions due to the high content of cationic charge associated with protonated amine groups on the polymer matrix. This is the first in-depth study investigating phosphate removal in vitro from aqueous solutions using commercially available sevelamer hydrochloride at physiological conditions of phosphate level, pH and temperature. The kinetic and thermodynamic parameters of phosphate binding onto the sevelamer hydrochloride particles were evaluated in order to define the binding process. A series of kinetic studies were carried out in order to delineate the effect of initial phosphate concentration, absorbent dose and temperature on the rate of binding. The results were analysed using three kinetic models with the best-fit of the experimental data obtained using a pseudo-second order model. Thermodynamic parameters provide in-depth information on inherent energetic changes that are associated with binding. Free energy ΔG°, enthalpy ΔH°, and entropy ΔS° changes were calculated in this study in order to assess the relationship of these parameters to polymer morphology. The binding reaction was found to be a spontaneous endothermic process with increasing entropy at the solid–liquid interface.

Kinetics, isotherm, thermodynamic, and adsorption mechanism studies of La(OH)3-modified exfoliated vermiculites as highly efficient phosphate adsorbents

La(OH)3-modified exfoliated vermiculites were fabricated, characterized, and investigated for phosphate removal in batch tests for the first time. The BET surface area of the La5EV adsorbent, which was synthesized in the solution consisting of 5.00mmol/g La/exfoliated vermiculite (EV), was significantly increased, accompanied with a larger pore diameter and greater total pore volume, as compared with the unmodified EV. The phosphate adsorption capacity of La5EV was approximately one order of magnitude higher than that of EV. Effects of initial phosphate concentration, contact time, temperature, pH, and co-existing ions on the adsorption capacity of La5EV were investigated in detail. The experimental equilibrium data were fitted better by using the Langmuir model (maximum adsorption capacity of 79.6mg P/g) than the Dubinin–Radushkevich or the Freundlich model, suggesting that the adsorption feature be monolayer. Meanwhile, the phosphate adsorption kinetics could be well described by the pseudo-second-order model, and the adsorption process might be controlled by boundary layer (film) diffusion. ΔG°, ΔH° and ΔS° were also determined, in which it was found that the phosphate adsorption onto La5EV was spontaneous and exothermic in nature. The phosphate adsorption of La5EV was pH-dependent; that it exhibited a high adsorption capacity in the pH range of 3.0–7.0. The presence of 0.1M CO32- caused a reduction in phosphate adsorption capacity by 54.3%. On the other side, the addition of F−, Cl−, NO3-, and SO42- had neglectable effects on its phosphate removal capacities. In the synthetic secondary treated wastewater with a low phosphate concentration of 2mg P/L, 97.9% of its final adsorption capacity reached in the first 10min and the phosphate concentration dramatically decreased below 50μg P/L. The spent La5EV could be regenerated and reused in phosphate adsorption; that could remove more than 70% phosphate in the 3rd adsorption–desorption cycle.

Novel hollow microspheres of hierarchical zinc–aluminum layered double hydroxides and their enhanced adsorption capacity for phosphate in water

Hollow microspheres of hierarchical Zn–Al layered double hydroxides (LDHs) were synthesized by a simple hydrothermal method using urea as precipitating agent. The morphology and microstructure of the as-prepared samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), nitrogen adsorption–desorption isotherms and fourier transform infrared (FTIR) spectroscopy. It was found that the morphology of hierarchical Zn–Al LDHs can be tuned from irregular platelets to hollow microspheres by simply varying concentrations of urea. The effects of initial phosphate concentration and contact time on phosphate adsorption using various Zn–Al LDHs and their calcined products (LDOs) were investigated from batch tests. Our results indicate that the equilibrium adsorption data were best fitted by Langmuir isothermal model, with the maximum adsorption capacity of 54.1–232 mg/g; adsorption kinetics follows the pseudo-second-order kinetic equation and intra-particle diffusion model. In addition, Zn–Al LDOs are shown to be effective adsorbents for removing phosphate from aqueous solutions due to their hierarchical porous structures and high specific surface areas.

Phosphate uptake behavior of ZnAlZr ternary layered double hydroxides through surface precipitation

Tetravalent Zr 4+ ion incorporated ZnAl hydrotalcite-like material with varying Zn/(Al + Zr) atomic ratio (2–4) and Al/Zr atomic ratio 0.7:0.3 with CO 3 2 - as interlayer anion were successfully synthesized and characterized by various physicochemical methods. The phosphate uptake studies were carried out over these materials by batch method with the objective of enhancing the uptake through creation of higher positive charge on brucite-like layers by the incorporation of Zr 4+. The studies revealed that ternary ZnAlZr hydrotalcites show good uptake capacity for phosphate, among which ZnAlZr4-HT depicts a maximum uptake of around 91 mgP/g. We observed that phosphate uptake results in the formation of layered hopeite mineral (Zn 3(PO 4) 3·4H 2O) on the surface of material by the surface precipitation of dissolved zinc ion through the outer-sphere complex formation of phosphate. The phosphate uptake increases with a decrease in Zn/Al and Zn/(Al + Zr) atomic ratios. Effects of initial phosphate concentration, contact time, adsorbent amount and temperature variation on phosphate uptake were studied. Co-presence of competitive anion like nitrate enhances the uptake of phosphate to 148 mgP/g. Recycle studies of the material shows a decrease in the uptake of phosphate with the number of cycles due to an increase in the crystallinity. Very high uptake of phosphate by these materials even in the presence of other anions/cations suggests their potential role in waste water remediation.

Production of polyhydroxyalkanoates from whey by Thermus thermophilus HB8

The thermophilic bacterium Thermus thermophilus HB8 is able to utilize lactose from whey-based media for the biosynthesis of polyhydroxyalkanoates (PHAs) under nitrogen limitation. T. thermophilus can utilize both, glucose and galactose, the products of lactose hydrolysis. When T. thermophilus HB8 was grown in culture media containing 24% (v/v) whey, PHA was accumulated up to 35% (w/w) of its biomass after 24 h of cultivation. The effect of initial phosphate concentration on the PHA production was also investigated. Using an initial phosphate concentration of 50 mM the PHA accumulation was enhanced. Analysis of the produced PHA from T. thermophilous HB8 grown in whey-based media revealed a novel heteropolymer consisting of the short chain length 3-hydroxyvalerate (3HV; 38 mol%) and the medium chain length, 3-hydroxyheptanoate (3HHp; 9.89 mol%), 3-hydroxynanoate (3HN; 16.59 mol%) and 3-hydroxyundecanoate (3HU; 35.42 mol%). Despite the low molecular weight of the produced PHA by T. thermophilus, whey could be an excellent substrate for the production of heteropolymers with unique properties.

Adsorption of phosphate from seawater on calcined MgMn-layered double hydroxides

Adsorptive properties of MgMn-3-300 (MgMn-type layered double hydroxide with Mg/Mn mole ratio of 3, calcined at 300 °C) for phosphate were investigated in phosphate-enriched seawater with a concentration of 0.30 mg-P/dm 3. It showed the highest phosphate uptake from the seawater among the inorganic adsorbents studied (hydrotalcite, calcined hydrotalcite, activated magnesia, hydrous aluminum oxide, manganese oxide ( δ-MnO 2)). The phosphate uptake by MgMn-3-300 reached 7.3 mg-P/g at an adsorbent/solution ratio of 0.05 g/2 dm 3. The analyses of the uptakes of other constituents (Na +, K +, Ca 2+, Cl −, and SO 2− 4) of seawater showed that the adsorbent had a markedly high selectivity for the adsorption of phosphate ions. Effects of initial phosphate concentration, temperature, pH, and salinity on phosphate uptake were investigated in detail by a batch method. The phosphate uptake increased slightly with an increase in the adsorption temperature. The adsorption isotherm followed Freundlich's equation with constants of log K F = 1.25 and 1 / n = 0.65 , indicating that it could effectively remove phosphate even from a solution of markedly low phosphate concentration as well as with large numbers of coexisting ions. The pH dependence showed a maximum phosphate uptake around pH 8.5. The pH dependence curve suggested that selective phosphate adsorption progresses mainly by the ion exchange of HPO 2− 4. The study on the effect of salinity suggested the presence of two kinds of adsorption sites in the adsorbent: one nonspecific site with weak interaction and one specific site with strong interaction. The effective desorption of phosphate could be achieved using a mixed solution of 5 M NaCl + 0.1 M NaOH (1 M = 1 mol/dm 3), with negligible dissolution of adsorbent. The adsorbent had high chemical stability against the adsorption/desorption cycle; it kept a good phosphate uptake even after the repetition of the seventh cycle.

Production of poly(3-hydroxybutyrate) by high cell density fed-batch culture of Alcaligenes eutrophus with phospate limitation

High cell density fed-batch fermentation of Alcaligenes eutrophus was carried out for the production of poly(3-hydroxybutyrate) (PHB) in a 60-L fermentor. During the fermentation, pH was controlled with NH(4)OH solution and PHB accumulation was induced by phosphate limitation instead of nitrogen limitation. The glucose feeding was controlled by monitoring dissolved oxygen (DO) concentration and glucose concentration in the culture broth. The glucose concentration fluctuated within the range of 0-20 g/L. We have investigated the effect of initial phosphate concentration on the PHB production when the initial volume was fixed. Using an initial phosphate concentration of 5.5 g/L, the fed-batch fermentation resulted in a final cell concentration of 281 g/L, a PHB concentration of 232 g/L, and a PHB productivity of 3.14 g/L . h, which are the highest values ever reported to date. In this case, PHB content, cell yield from glucose, and PHB yield from glucose were 80, 0.46, and 0.38% (w/w), respectively.

Effects of initial phosphate concentration on physiological aspects of suspension cultures of rice cells: A kinetic study

The effects of initial phosphate concentration ( P i) on the kinetics of cell growth and the consumption of major nutrients in suspension cultures of rice ( Oryza sativa) cells were investigated. The results indicate that the cell growth kinetics could be described by the Monod equation for phosphorus-limited cultures. A correlation between phosphorus consumption and specific growth rate of the cells was successfully established based on the changes of extra- and intracellular phosphorus. In addition, P i and the free pool of intracellular phosphorus ( C F) were correlated with the cell yield against sugar, the consumption rate of nitrogen sources, and the nitrate utilization percentage.

Effect of initial phosphate concentration on cell growth and ginsenoside saponin production by suspended cultures of panax notoginseng

Effects of initial phosphate concentration on the growth, ginsenoside saponin production, and the consumption of sugar and nitrogen sources by suspended cells ofPanax notoginseng (Burk) F. H. Chen were investigated in a 250-mL shake flask. The results indicate that by increasing the initial phosphate concentration in the medium in the range of 0–1.25 mM, both the cell growth and the saponin accumulation were greatly improved, and the utilization of sugar and nitrogen sources was also increased. The highest production, productivity, and yield of ginsenosides obtained were 0.98 g/L, 45.5 mg/L/d, and 0.030 g/g at 1.25 mM of initial medium phosphate. At a relatively higher level of medium phosphate, i.e., 2.0 mM, the product accumulation was inhibited to some degree, although the cell growth was not.