Yuting Zhou

Removal of Cu2+ from aqueous solution by chitosan-coated magnetic nanoparticles modified with α-ketoglutaric acid.

Chitosan-coated magnetic nanoparticles (CCMNPs), modified with a biodegradable and eco-friendly biologic reagent, alpha-ketoglutaric acid (alpha-KA), was used as a magnetic nanoadsorbent to remove toxic Cu(2+) ions from aqueous solution. The prepared magnetic nanoadsorbents were characterized by FTIR, TEM, VSM, XRD, and EDS. Factors influencing the adsorption of Cu(2+), e.g., initial metal concentration, initial pH, contact time and adsorbent concentration were investigated. TEM images show that the dimension of multidispersed circular particles is about 30 nm and no marked aggregation occurs. VSM patterns indicate superparamagnetic properties of magnetic nanoadsorbents. EDS pictures confirm the presence of the Cu(2+) on the surface of magnetic nanoadsorbents. Equilibrium studies show that Cu(2+) adsorption data follow Langmuir model. The maximum adsorption capacity (q(max)) for Cu(2+) ions was estimated to be 96.15 mg/g, which was higher than that of pure CCMNPs. The desorption data show no significant desorption hysteresis occurred. In addition, the high stability and recovery capacity of the chitosan-coated magnetic nanoparticles modified with alpha-ketoglutaric acid (alpha-KA-CCMNPs) suggest that these novel magnetic nanoadsorbents have potential applications for removing Cu(2+) from wastewater.

Removal of Cu2+ from aqueous solution by adsorption onto a novel activated nylon-based membrane

A novel activated nylon-based membrane was prepared and applied as an adsorbent for the removal of Cu2+ from aqueous solutions. It involved three stages: (i) deposition of a chitosan layer that functionalized the nylon membrane, (ii) cross-linking with epichlorohydrin to stabilize the polymer layer and enabling grafting, and (iii) iminodiacetic acid grafting. SEM and EDX techniques were used to characterize the composition of the membranes. Dynamic adsorption experiments on membranes were carried out at various pH values, contact times, adsorption dosages and initial metal concentrations to determine optimum membrane adsorption properties. The adsorption isotherm relating to Cu2+ fitted the Langmuir equation and an adsorption equilibrium constant and adsorption capacity of 2.345x10(-3)mg/ml and 10.794mg/g were determined, respectively. The experimental data was analyzed using two adsorption kinetic models, pseudo-first-order and pseudo-second-order with the latter system providing the best fit. Finally complete regeneration of the activated nylon membrane was possible using 100mmol/l Na2EDTA.

Affinity Adsorption of Bromelain on Reactive Red 120 Immobilized Magnetic Composite Particles

A magnetic dye affinity adsorbent was prepared by coating the magnetic nanoparticles (MNPs) with chitosan (CS), which significantly decreased the non-specifically adsorbing protein. Following this, Reactive Red 120 (Red 120), chosen as a dye affinity ligand, was immobilized onto the chitosan-coated magnetic nanoparticles (CS-MNPs) to obtain the specific protein adsorption. The prepared functionalized adsorbents were characterized by SEM, FTIR, XRD, VSM, and elementary analysis. Factors influencing the adsorption of bromelain, e.g., initial protein concentration, medium pH, and ionic strength were investigated. The adsorption isotherm fitted the Freundlich model well. The regeneration experiment showed that the affinity superparamagnetic particles were suitable for bromelain adsorption.

Papain Adsorption on Chitosan-Coated Nylon-Based Immobilized Metal Ion (Cu2+, Ni2+, Zn2+, Co2+) Affinity Membranes

A novel immobilized metal affinity membrane was prepared for papain adsorption in this article. Higher papain adsorption capacity between 43-67 mg/g was observed and the adsorption isotherm fitted the Freundlich equation. Experimental data were analyzed using two adsorption kinetic models. The pseudo-second-order kinetic model provided better correlation to the experimental results. A significant amount of the adsorbed papain was eluted by 1.0 M NaSCN at pH 5.0 for all affinity membranes. It was concluded that the novel chitosan-coated nylon-based immobilized metal ion affinity membrane could be applied for the large-scale isolation of papain without resulting in enzyme denaturation.

Improving the Stability of Cellulase by Immobilization on Chitosan-Coated Magnetic Nanoparticles Modified alpha-Ketoglutaric Acid

The application of cellulases in various industries demands highly stable enzymes, able to perform at extreme pH values and temperatures. In this study, the cellulase, which was immobilized on the chitosan-coated magnetic nanoparticles modified with alpha-ketoglutaric acid (alpha-KA-CCMNPs), exhibited a broader pH range of high activity and the loss of the activity of immobilized cellulase was lower than that of free cellulase. And the optimal temperature for immobilized cellulase was 50degC, whereas that for free cellulase was 40degC. Meanwhile, the immobilized cellulase showed better thermal stability than free cellulase at high temperature range. In addition, the storage stability of the cellulase was improved greatly after it was immobilized on the surface of alpha-KA-CCMNPs.

Isotherm, Kinetic and Thermodynamic Analysis of Bromelain Adsorption on Reactive Blue 4 Immobilized Composite Membranes

The behavior of bromelain adsorption on the dyeligand affinity membrane was investigated at 277,298 and 310K, which was chitosan (CS) coated to decrease the non-specific adsorption of protein. Reactive Blue 4 was immobilized onto the CS-coated nylon membrane as an affinity ligand. In order to examine the rate limiting step of Reactive Blue 4-immobilized composite membrane adsorption, the two adsorption kinetic model: the pseudo-first-order and the pseudo-second-order were tested with the experiment data. Results indicated that Freundlich isotherm was able to adequately describe the adsorption of bromelain on dye affinity membranes. It was also found that the pseudo-first-order kinetic model described the bromelain adsorption process with a good fitting. Keywords-adsorption; bromelain; Reactive Blue 4; isotherm; kinetic; thermodynamic

Papain Immobilization on Chitosan-Coated Nylon Membrane: Preparation and Its Application in Cystatin Separation

Nylon membranes are first hydrolyed with dilute HCl and then treated with chitosan before being used as the affinity carrier. Papain as a ligand has been immobilized on the activated membranes with glutaraldehyde as a crosslinking agent. The factors involving with the activity of immobilized papain, such as concentration of glutaraldehyde, pH, temperature, reaction time, and the amount of added papain have been studied. The results show that the optimum conditions for the preparation of immobilized papain nylon affinity membranes are as follows: pH 9.0, 0.5% glutaraldehyde solution, the concentration of added papain is 10 mg/ml, the reaction time is 6 h at 45degC. The nylon membrane prepared is then used to purify cystatin from potato juice, and shows that they are high efficiency affinity membranes base for cystatin separation.