Biosorption of cadmium and nickel by functionalized husk of Lathyrus sativus

The husk of Lathyrus sativus (HLS) has been functionalized by introducing thio groups with the help of carbon disulphide treatment in alkaline environment. Elemental analysis indicates that sulphur content of the functionalized biomass increases to 3.7% from 0.36% of the pristine biomass suggesting the incorporation of thio group on HLS. A conspicuous change in the surface morphology of the biomass due to functionalization is depicted by SEM images. EDX data support the introduction of sulphur group on the HLS. The involvement of the hydroxyl groups mainly in the functionalization process is demonstrated by Fourier transform infrared (FTIR) spectroscopic study. The adsorption capacity of the functionalized biomass with respect to cadmium and nickel is observed to increase by about 50% compared to that of pristine one. Similar to the case of unmodified HLS the adsorption process involving the functionalized one obeys Langmuir isotherm model and attains equilibrium in 10 min compared with 60 min in the case of unmodified biomass.     

卟啉钒在改性高岭土上的吸附行为及机理研究

利用酸改性和负载钼的酸改性高岭土作为吸附剂研究了环己烷中的卟啉钒(钒氧-2,3,7,8,12,13,17,18-八乙基卟啉,VO-OEP)在这两种吸附剂上的吸附行为,从热力学角度探讨了吸附机理。结果表明,两种吸附剂对卟啉钒的吸附符合Langmuir吸附等温线,卟啉钒单层吸附在改性高岭土上;吸附表现为自发热过程,吸附热均大于40 kJ/mol,说明吸附形成了化学键。     

Adsorption behavior of rice husk for the decontamination of chromium from industrial effluents

Rice husk, an agricultural waste product, was studied as a potential decontaminant for chromium in the effluents of leather tanning industries. Physico-chemical parameters such as selection of appropriate electrolyte, shaking time, concentration of adsorbent and adsorbate were studied to optimize the best conditions in which this material can be utilized on commercial scale for the decontamination of effluents. The radiotracer technique was used to determine the distribution of chromium. In certain cases atomic absorption spectrophotometry was also employed. Maximum adsorption was observed at 0.01 mol·dm⁻³ acid solutions (HNO₃, HCl, H₂SO₄ and HClO₄) using 3.0 g of adsorbent for 2.73·10⁻³ mol·dm⁻³ chromium concentration in five minutes equilibration time. Studies show that the adsorption decreases with the increase in the concentrations of all the acids. The adsorption data follows the Freundlich isotherm over the range of 2.73·10⁻³ to 2.73·10⁻² mol·dm⁻³ chromium concentration. The characteristic Freundlich constants, i.e., 1/n=0.86±0.06 andA=2.35±0.06 mmol·g⁻¹ have been computed for the sorption system. Thermodynamic parameters, i.e., ΔG ⁰, ΔS ⁰ and ΔH ⁰ have also been calculated for the system. Application of the method to a test case of a medium size industry showed that 21 kg of rice husk was sufficient to maintain the NEQS limits of chromium for industrial effluents.     

Kinetic Spectrophotometric Method for Determination of Oxalic Acid and Its application in Lathyrus sativus

Oxalic acid is one of the most common nutrient chelators in the human diet found in many vegetables, such as mushroom, spinach, fresh kidney beans, rhubarb leaves and beet leaves. Some recent reports demonstrate that oxalate plays an important role in resistance stress metabolism and steady state regulation in plant. [1]     

Adsorption behavior of linear and cyclic genetically engineered platinum binding peptides

Recently, phage and cell-surface display libraries have been adapted for genetically selecting short peptides for a variety of inorganic materials. Despite the enormous number of inorganic-binding peptides reported and their bionanotechnological utility as synthesizers and molecular linkers, there is still a limited understanding of molecular mechanisms of peptide recognition of and binding to solid materials. As part of our goal of genetically designing these peptides, understanding the binding kinetics and thermodynamics, and using the peptides as molecular erectors, in this report we discuss molecular structural constraints imposed upon the quantitative binding characteristics of peptides with an affinity for inorganics. Specifically, we use a high-affinity seven amino acid Pt-binding sequence, PTSTGQA, as we reported in earlier studies and build two constructs: one is a Cys-Cys constrained "loop" sequence (CPTSTGQAC) that mimics the domain used in the pIII tail sequence of the phage library construction, and the second is the linear form, a septapeptide, without the loop. Both sequences were analyzed for their adsorption behavior on Pt thin films by surface plasmon resonance (SPR) spectroscopy and for their conformational properties by circular dichroism (CD). We find that the cyclic peptide of the integral Pt-binding sequence possesses single or 1:1 Langmuir adsorption behavior and displays equilibrium and adsorption rate constants that are significantly larger than those obtained for the linear form. Conversely, the linear form exhibits biexponential Langmuir isotherm behavior with slower and weaker binding. Furthermore, the structure of the cyclic version was found to adopt a random coil molecular conformation, whereas the linear version adopts a polyproline type II conformation in equilibrium with the random coil. The 2,2,2-trifluoroethanol titration experiments indicate that TFE has a different effect on the secondary structures of the linear and cyclic versions of the Pt binding sequence. We conclude that the presence of the Cys-Cys restraint affects both the conformation and binding behavior of the integral Pt-binding septapeptide sequence and that the presence or absence of constraints could be used to tune the adsorption and structural features of inorganic binding peptide sequences.     

Adsorption of isopropanol on a nickel oxide

Adsorption isotherms of isopropanol are obtained in the temperature range of 243 to 303 K on the initial surface of nickel oxide after its treatment in high-frequency plasma in Ar and glow-discharge plasma in O₂. It is found that such treatment lower the isosteric heat and differential entropy of reversible adsorption, along with the general acidity of the oxide’s surface. At low degrees of filling, isotherms are described by the equation of induced adsorption. It is established that adsorbed molecules of isopropanol take negatively charged and two positively charged forms. Lewis acidic centers of various strengths can serve as adsorption centers in addition to centers of other types.     

Adsorption mechanism and acidic behavior of naphthazarin on Ag nanoparticles studied by Raman spectroscopy

Surface-enhanced Raman scattering (SERS) spectroscopy is applied in this work to the study of the adsorption of naphthazarin (NZ) on Ag nanoparticles. Spectra recorded at different excitation wavelengths and pHs revealed that this molecule is adsorbed on the metal through several mechanisms. Two main types of adsorbed molecules can be identified that correspond to neutral and ionized NZ, which may be physisorbed or chemisorbed on the metal. The existence of these different forms can be due to different binding sites on the surface or to the formation of a multilayer architecture on the metal surface giving rise to different adsorbate states. Although the amount of the ionized molecule attached on the surface is higher at neutral pH, the neutral molecule may also exist even at very high pH. The amount of neutral NZ increases with the time and also as the NZ concentration is raised or as the dimethylsulfoxide (DMSO) concentration existing in the medium is increased.     

Adsorption of isopropanol on a nickel catalyst

The adsorption isotherms of isopropanol on a Ni catalyst (15 wt % on SiO₂) in the temperature range of 273–303 K are determined. An increase in the isosteric heat of adsorption and entropy of adsorption after treating the catalyst with high frequency plasma in hydrogen and adding 1.5 wt % of Ce is detected, with treatment involving glow discharge plasma in Ar and O₂ having virtually no impact on these values. At a low degree of surface filling, the adsorption isotherms are described by the equation of induced adsorption. It is concluded that adsorbed isopropanol molecules are present in two forms: positively and negatively charged.     

Analysis of beta-N-oxalyl-L-alpha,beta-diaminopropionic acid and homoarginine in Lathyrus sativus by capillary zone electrophoresis.

A simple capillary zone electrophoresis (CZE) method has been developed for the simultaneous quantitative determination of beta-N-oxalyl-L-alpha,beta-diaminopropionic acid (beta-ODAP) and homoarginine in Lathyrus sativus (LS; grass pea). A new Na2B4O7-Na2SO4 run buffer was used and the pH was 9.20, contents of beta-ODAP and homoarginine in crude extracts of LS plant material were determined with this method, the RSDs of peak areas of beta-ODAP and homoarginine were 2.62% and 3.61%, respectively. It was found that the equilibrium concentration ratio of alpha- and beta-ODAP decreased from 34.5/65.5 to 28.6/71.4 when the pH of the solution increased from pH 3.0 to pH 11.0.     

NaOH改性稻壳对亚甲基蓝的吸附性能研究

采用NaOH改性稻壳为吸附剂,探究稻壳在不同条件下对亚甲基蓝的吸附性能.同时利用比表面积测定、扫描电镜、红外光谱等表征手段对改性前后的吸附剂进行物化特性、样品形貌等分析.结果 表明,采用4 wt.％NaOH改性稻壳,亚甲基蓝溶液的初始浓度为80 mg·L-1、pH为6.0、温度为25℃、震荡时间为12 h、吸附剂用量为...     

Fabrication and characterization of Grass pea (Lathyrus sativus) protein isolate-Alyssum homolocarpum seed gum complex coacervate

The present work was carried out to fabricate Grass pea (Lathyrus sativus) protein isolate (GPPI) and Alyssum homolocarpum seed gum (AHSG) complex coacervate and investigate its morphological and structural properties. Formation of complex coacervates were studied by zeta potentiometry and turbidimetric analysis as function of different pHs (7.0–2.0) and GPPI to AHSG ratios (3:1 to 1:3). The critical pH values associated with the formation of soluble (pH_c) and insoluble (pH_φ1) complexes, and complete dissociation (pH_φ2) at GPPI to AHSG ratio (1:1) were found to be 4.8, 4.0, and 2.5, respectively. Formation of insoluble complex coacervate was maximum at pH 3.2 and GPPI to AHSG ratio of 1:1, where the highest yield (69%) was observed. Scanning electron microscopic (SEM) demonstrated that GPPI-AHSG complex had a rough branched-like structure. Results also showed that the complexation between GPPI and AHSG were formed through the electrostatic interaction and hydrogen bonding. Circular dichroism spectroscopy (CD) indicated that the β-sheet and random coil content in GPPI increased when AHSG molecules were added to protein solution. The fading of pure peaks of GPPI and AHSG in X-Ray diffraction (XRD) patterns of GPPI-AHSG complexes confirmed the alterations in the physical state of mixture from crystalline to amorphous. GPPI-AHSG complex coacervates had lower weight loss compared to individual GPPI and AHSG.     

Adsorption of nickel on synthetic hydroxyapatite from aqueous solutions

The sorption of nickel on synthetic hydroxyapatite was investigated using a batch method and radiotracer technique. The hydroxyapatite samples used in experiments were a commercial hydroxyapatite and hydroxyapatite of high crystallinity with Ca/P ratio of 1.563 and 1.688, respectively, prepared by a wet precipitation process. The sorption of nickel on hydroxyapatite was pH independent ranging from 4.5 to 6.5 as a result of buffering properties of hydroxyapatite. The adsorption of nickel was rapid and the percentage of Ni sorption on both samples of hydroxyapatite was >98 % during the first 15–30 min of the contact time for initial Ni²⁺ concentration of 1 × 10^?4 mol dm^?3. The experimental data for sorption of nickel have been interpreted in the term of Langmuir isotherm and the value of maximum sorption capacity of nickel on a commercial hydroxyapatite and hydroxyapatite prepared by wet precipitation process was calculated to be 0.184 and 0.247 mmol g^?1, respectively. The sorption of Ni²⁺ ions was performed by ion-exchange with Ca²⁺ cations on the crystal surface of hydroxyapatite under experimental conditions. The competition effect of Co²⁺ and Fe²⁺ towards Ni²⁺ sorption was stronger than that of Ca²⁺ ions. NH₄ ⁺ ions have no apparent effect on nickel sorption.     

Adsorption of dicarboxylic acids on lithiated nickel oxide electrode

Adsorption of dicarboxylic acids on NiO electrodes was studied by means of the galvanostatic transient method, mainly for oxalic acid. The oxalate or hydrogen oxalate anion or both were concluded to adsorb on the electrode. The adsorption was maximal at a potential less positive than the flat-band potential of the electrode, owing to preferential adsorption of hydroxyl anion in the region above the maximum adsorption potential. The quantity of adsorption was dependent on carrier concentration of the electrode, and high for the electrode of high carrier concentration. This phenomenon is connected to the charged condition of the electrode that when the maximum adsorption takes place, positively charged sites remain on the surface of the electrode which is charged negatively as a whole and the amount of the sites is much more different between the electrodes of different N than their bulk carrier concentrations. Adsorptions of malonic and succinic acid were distinctly low compared with that of oxalic acid. The adsorbability was in the order; oxalic acid>malonic acid>succinic acid. This order was in accord with the stability constants of nickel dicarboxylic acid chelates.     

Adsorption behavior, thermodynamics, and mechanism of phenol on polymeric adsorbents with amide group in cyclohexane

Macroporous cross-linked poly(N-methyl-N-p-vinylbenzylacetamide) (PMVBA), poly(N-methyl-N-p-vinylbenzylcaprolactam) (PMVBC), and poly(N-methyl-N-p-vinylbenzylurea) (PMVBU) were synthesized and their adsorption behavior for phenol in cyclohexane was investigated. The results indicated that the adsorption capacities of phenol on the three adsorbents followed the order PMVBU > PMVBA > PMVBC. Adsorption isotherms of phenol on the three polymeric adsorbents were measured and correlated to a Freundlich isotherm. Adsorption enthalpy, adsorption Gibbs free energy, and adsorption entropy were calculated using thermodynamic function relationships. It was found that the adsorption enthalpy of phenol on PMVBU was almost twice that on PMVBA and PMVBC. Analysis of the adsorption mechanism suggested that hydrogen bonding was the primary driving force for phenol adsorbed on the adsorbents in cyclohexane, and multiple hydrogen bonding was involved for PMVBU with phenol.