Effects Of Initial Solution pH Research Articles

Sorption of Al (III) from aqueous solution by fresh macrophyte alligator weed: Equilibrium and kinetics

The removal of Al (III) ions from aqueous solution by locally abundantly low-cost fresh macrophyte, alligator weed, was examined in batch system. Effect of initial solution pH on Al (III) adsorption was investigated and the Al (III) species present in aqueous solution were identified. The main functional groups of the alligator weed were characterized by Fourier transform infrared spectrometer (FT-IR). The equilibrium data fitted to Freundlich and Langmuir isotherms satisfactorily. The pseudo-second-order equation fitted the kinetic data very well. The intraparticle diffusion played an important role in the Al (III) sorption process. Al (III) ions were favorably adsorbed by alligator weed and the values of K f and 1/ n (Freundlich constant) at 25 °C and pH 3.5 were found as 1.9963 (mg/g)/(mg/L) 1/ n and 0.7875, respectively, which are comparable to those of granular activated carbon (2.20 (mg/g)/(mg/L) 1/ n and 0.8695, respectively).

Dynamic studies and pseudo-second order modeling of copper(II) biosorption onto pine cone powder

The chemical interaction between biosorbent functional groups and metal ion species in solution can slightly be altered by chemical treatment of biosorbent surface. The biosorbent kinetics and mechanism for copper(II) biosorption onto pine cone powder and 0.15moldm−3 NaOH treated pine cone powder were determined during batch kinetics with the variation in biosorption temperature and initial copper(II) concentration. Results from this study revealed that surface diffusion of copper(II) is not rate-controlling as observed by the failure of both the pseudo-first and modified pseudo-first order model to discribe the kinetic data. The pseudo-second order model gave a better description of the kinetic data and was able to correlate the model constants with process variables for both samples. Activation energies and thermodynamic parameters of activation obtained from the pseudo-second order model all indicate that the mechanism for copper(II) biosorption on both samples differ. The diffusion partten is complex for the biosorption process, involving pore and film diffusion in the rate determining step and did not follow the same pattern for both samples. Pseudo-isotherms were generated to confirm the fit of the experimental data to the predictions of the pseudo-second order model. It was observed that the generated isotherm data fitted better to the Pseudo-Langmuir-1 isotherm indicating that biosorption was indeed a monolayer coverage of the biosorbent surface confirming the applicability of this model. Effect of initial solution pH and desorption studies confirm the predominance of a slightly different mechanism using both samples.

Biosorption of Cd(II), Ni(II) and Pb(II) from Aqueous Solution by Dried Biomass of Aspergillus niger: Application of Response Surface Methodology to the Optimization of Process Parameters

AbstractIn this study, the biosorption of Cd(II), Ni(II) and Pb(II) on Aspergillus niger in a batch system was investigated, and optimal condition determined by means of central composite design (CCD) under response surface methodology (RSM). Biomass inactivated by heat and pretreated by alkali solution was used in the determination of optimal conditions. The effect of initial solution pH, biomass dose and initial ion concentration on the removal efficiency of metal ions by A. niger was optimized using a design of experiment (DOE) method. Experimental results indicated that the optimal conditions for biosorption were 5.22 g/L, 89.93 mg/L and 6.01 for biomass dose, initial ion concentration and solution pH, respectively. Enhancement of metal biosorption capacity of the dried biomass by pretreatment with sodium hydroxide was observed. Maximal removal efficiencies for Cd(II), Ni(III) and Pb(II) ions of 98, 80 and 99% were achieved, respectively. The biosorption capacity of A. niger biomass obtained for Cd(II), Ni(II) and Pb(II) ions was 2.2, 1.6 and 4.7 mg/g, respectively. According to these observations the fungal biomass of A. niger is a suitable biosorbent for the removal of heavy metals from aqueous solutions. Multiple response optimization was applied to the experimental data to discover the optimal conditions for a set of responses, simultaneously, by using a desirability function.

Biosorption of Acid Blue 5 by Biomass Derived from Eichhornia crassipes: Batch and Column Studies

Biosorption of Acid Blue 5 dye by the Eichhornia crassipes was investigated in batch and column studies. Batch experiments were conducted to study the effect of initial solution pH and dye concentration. Langmuir and Freundlich sorption models were used to represent the equilibrium data. Experimental breakthrough curves in a column were obtained with bed height (5, 10 and 15 cm), flow rate (20, 25 and 30mL/min) and initial dye concentration (50, 75 and 100 mg/L). An increase in bed height and initial dye concentration favors the dye biosorption, while the minimum flow rate produced maximum dye biosorption. It was observed that the uptake of Acid Blue 5 using a bed height of 15 cm, flow rate of 20 mL/min and initial dye concentration of 100 mg/L was found to be more when compared to all other bed height, flow rate and initial dye concentration studied in the present investigation. The Bed Depth Service Time (BDST) model was used for the evaluation of continuous sorption data.

Comparison of strontium and calcium adsorption onto composite magnetic particles derived from Fe 3O 4 and bis(trimethoxysilylpropyl)amine

The adsorption of strontium and calcium ions by composite magnetic particles derived from Fe 3O 4 and bis(trimethoxysilylpropyl)amine (TSPA) were comparatively studied. The effects of initial solution pH, ionic strength, initial strontium and calcium ion concentration, and temperature on the equilibrium adsorption amount of both strontium and calcium ions, and on the separation factor between strontium and calcium ions were investigated comprehensively. The adsorption occurs rapidly in the first 30 min. In general, the equilibrium adsorption amount of both strontium and calcium ions was found to increase with the increase in initial ion concentration and initial solution pH, but to decrease gradually with the increase in ionic strength. The equilibrium adsorption amount of strontium ions increases with the increase in adsorption temperature. However, the effect of temperature on the adsorption of calcium ions presents a complicated situation. Strontium ions have a higher affinity to the composite particles than calcium ions. The separation factor between strontium and calcium ions increases with the increase in adsorption temperature, but is not sensitive to ionic strength. The suitable experimental conditions for the separation between strontium and calcium ions are: initial solution pH 7–8, lower ionic strength, and higher adsorption temperature.

NaNO 2/FeCl 3 catalyzed wet oxidation of the azo dye Acid Orange 7

A combination of ferric chloride and sodium nitrite significantly improved the wet oxidation of the azo dye Acid Orange 7 (AO7) in acid aqueous media (pH 2.6) under moderate conditions ( T = 150 °C; oxygen pressure = 0.5 MPa). To evaluate the catalytic system, wet oxidation of AO7 was carried out at temperatures between 90 and 150 °C and oxygen pressures ranging from 0.1 to 0.5 MPa. The effect of initial solution pH from 2.6 to 11.4 and the amount of catalyst on the degradation of AO7 were also investigated. AO7 initial concentration was kept 200 mg L −1. The degradation process was monitored by UV–visible spectroscopy, HPLC, IC (ion chromatography), GC–MS and TOC analysis. At 150 °C and 0.5 MPa oxygen pressure, 56% TOC was removed after 4 h of treatment, while no obvious TOC removal were achieved without catalyst at the same experimental condition. The main degradation products were some small organic acids: formic acid, acetic acid, pyruvic acid, oxalic acid, succinic acid (identified and quantified by IC) and phthalic acid (identified by GC–MS).

Modelling the kinetics and equilibrium properties of cadmium biosorption by river green alga and water hyacinth weed

Cadmium biosorption properties of non-living, dried river green alga from a river source, and water hyacinth weed, Eichhornia crassipes from a lake in Zimbabwe have been investigated. The cadmium uptake was found to depend on initial pH, uptake being apparently minimal at low pH values and increasing with an increase in pH. Cadmium biosorption kinetics by both samples is fast, with 80% of total uptake occurring within 60 min. The effect of initial solution pH and initial cadmium concentration on cadmium biosorption from a cadmium solution has been studied. The data for algal biomass fitted the Langmuir monolayer adsorption isotherm, while the biosorption of the metal by water hyacinth weed fitted the Freundlich adsorption isotherm with 1/n values all less than 1. Maximum metal uptake capacities were recorded using 0.35 g of biomass and a 250 mg L−1 cadmium solution at pH 6.5 and at 25°C and these were about 85 and 50 mg L−1 for water hyacinth weed and green alga, respectively, showing that water hyacinth weed offered a greater potential for cadmium uptake. The absorption was described by pseudo-second order rate model and the rate constant and equilibrium sorption capacity are reported.

Effect of initial solution pH on the degradation of Orange II using clay-based Fe nanocomposites as heterogeneous photo-Fenton catalyst

Effect of initial solution pH on the discoloration and mineralization of 0.2 mM Orange II by using two clay-based Fe nanocomposites (Fe-B (Fe supported on bentonite clay) and Fe-Lap-RD (Fe supported on laponite clay)) as catalysts was studied in detail. It was found that the initial solution pH not only influences the photo-catalytic activity of Fe-B and Fe-Lap-RD but also the Fe leaching from the two catalysts. Both catalysts show the best photo-catalytic activity at an initial solution pH of 3.0, and the activity of the catalysts decreases as the initial solution pH increases. At optimal conditions, 100% discoloration and mineralization of 0.2 mM Orange II are achieved in 60 and 120 min reaction in the presence of 10 mM H 2O 2, 1.0 g/L Fe-B, and 1×8 W UVC at initial solution pH of 3.0. 100% discoloration and 90% mineralization of 0.2 mM Orange II are achieved when Fe-Lap-RD is used as catalyst under the same conditions. Both catalysts also display a reasonable good photo-catalytic activity and negligible Fe leaching at an initial solution pH of 6.6 that is very close to neutral pH. This characteristic makes it possible for the Fe-B and Fe-Lap-RD to have a long-term stability. It also becomes feasible for the photo-Fenton process to treat the original wastewater without the need to pre-adjust the solution pH.

Biosorption of Acid Blue 15 using fresh water macroalga Azolla filiculoides: Batch and column studies

The ability of fresh water macroalga Azolla filiculoides to biosorb Acid Blue 15 from aqueous solution was investigated in batch and column studies. Batch experiments were conducted to study the effect of initial solution pH and dye concentration. Langmuir and Freundlich isotherm models were used to fit the equilibrium data. The maximum dye uptake of 116.28 mg/g was observed at pH 7, according to Langmuir model. In column experiments, effects of bed height (15–25 cm), flow rate (5–15 ml/min) and initial dye concentration (50–100 mg/l) on dye removal were studied. An increase in bed height and initial dye concentration favors the dye biosorption, while the minimum flow rate produced maximum dye biosorption. At optimum bed height (25 cm), flow rate (5 ml/min) and initial dye concentration (100 mg/l), A. filiculoides exhibited an uptake of 35.98 mg/g of Acid blue 15. The Bed Depth Service Time model and the Thomas model were used to analyze the column experimental data and the model parameters were evaluated.

Fusion Peptide−Phospholipid Noncovalent Interactions As Observed by Nanoelectrospray FTICR−MS

Viral infections are propagated by the fusing of the viral membrane with a host cell membrane. Initiation of the fusion process occurs upon perturbation of the membrane of the cell under attack by a subunit of the viral protein known as a fusion peptide. Fusion peptides must insert into the lipid-rich host cell membrane to initiate rupture and merging of the two entities, but much remains unknown about the details of the fusion process. We present detailed electrospray mass spectrometry studies of binding specificities of model fusion peptides P294 and P326 with cell membrane phospholipids, i.e., phosphatidylcholines (PCs, such as 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)) and phosphatidylglycerols (PGs, such as 1,2-dimyristoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (DMPG)). The fusion peptides clearly bind more strongly to negatively charged DMPG than to zwitterionic DMPC. Detected binding between P294/P326 and PC/PG in 100% aqueous solution was disrupted by addition of methanol, which is known to weaken hydrophobic interactions; a higher percentage of methanol was needed to destroy a stronger initial binding. Further increases in the methanol volume fraction generally resulted in a reappearance of peptide-lipid binding, with binding strength quotients of 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC)/1,2-dilauroyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (DLPG)-peptide complexes rising more steeply than those of DMPC/DMPG-peptide complexes. Compared to fusion peptides P294 and P326, a hydrophilic peptide, fibrinopeptide B, showed much weaker affinity for zwitterionic DMPC, but had moderate binding affinity to negatively charged DMPG in 100% aqueous solutions. However, upon progressive addition of methanol, this hydrophilic peptide showed only a minor initial decrease in binding to DMPG before the detected binding eventually increased. These results contrast with those obtained for the hydrophobic peptides, and offer corroborative evidence that hydrophobic interactions play a key role in the mass spectrometrically observed binding between fusion peptides and phospholipids. Because the rate of viral infection has been found to be pH-dependent, the effect of initial solution pH on peptide-lipid binding was also studied. As the pH was lowered, P326-DMPC binding had a steep and immediate weakening, whereas the P294-DMPC binding was slightly strengthened at pH 3.7 and then gradually weakened with a further decrease in pH. Both P326 and P294 exhibited affinities toward unsaturated lipids; (18:1)PC bound slightly more strongly to P294 than (18:3)PC. These experiments offer further evidence of the ability of electrospray mass spectrometry to provide binding information concerning noncovalent interactions that were established principally by the hydrophobic effect in solution.