Dengxin Li

Supported cobalt oxide on graphene oxide: highly efficient catalysts for the removal of Orange II from water.

The current paper investigated the removal of the azo dye Orange II from water using advanced oxidation processes based on sulfate radicals. The cobalt oxide catalyst immobilized on graphene oxide (GO) can activate peroxymonosulfate (PMS) for the degradation of Orange II in water. The Co(3)O(4)/GO catalyst system was characterized via X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, and X-ray spectroscopy. Results showed that Co(3)O(4) was distributed on GO. The Co(3)O(4)/GO catalyst system exhibited high activity in Orange II oxidation when the Co(3)O(4)/GO catalyst has an optimum Co(3)O(4) loading. In addition, 100% decomposition could be achieved within 6 min with 0.2mM Orange II, 0.1 g L(-1) catalyst, and 2mM PMS. Meanwhile, inductively coupled plasma analysis revealed that the leach of cobalt ions was low. The catalyst also exhibited stable performance after several rounds of regeneration. Several operational parameters, such as catalyst amount, oxidant amount, pH, temperature, and oxidation rate, affected the degradation of Orange II.

Studies on the properties of graphene oxide–alkaline protease bio-composites

Graphene oxide (GO) nanosheets as functional material have a unique planar structure and intriguing mechanical that have attracted intensive interests recently. A method was developed for the immobilization protease on GO sheets using glutaraldehyde as cross-linking reagent. The results showed that the thermostability and reusability of immobilized protease have been obviously improved compared to the free enzyme. However, there was no significant change in optimum pH value between the free and immobilized protease. The immobilized protease exhibited good operational stability. The apparent K(m) and V(max) for free and immobilized alkaline protease were determined, and the bio-catalytic activity was not impaired by immobilization.

Adsorption of Sn(II) on expanded graphite: kinetic and equilibrium isotherm studies

AbstractExpanded graphite (EG) was prepared by microwave irradiation at 1000 W for 60 s. EG is a novel adsorbent for Sn(II) adsorption and its ability to remove Sn(II) ions from wastewater was investigated. To characterize the adsorptive characteristics of the produced EG, the microstructures of the resultant EG were observed using scanning electron microscopy. Chemical characterization of the surface resultant EG was studied by Fourier transform infrared spectroscopy. The effects of pH, adsorbent dosage, initial concentration, temperature, and contact time on the adsorption surface were studied using the batch process technique. The data fitted with the Langmuir equilibrium isotherm and pseudo-second-order kinetics. The maximum adsorption capacity of Sn(II) on the resultant EG was 378.78 mg g−1.

Migration and transformation rule of heavy metals in sludge during hydrolysis for protein extraction

The content and speciation of heavy metals can fundamentally affect the hydrolysis of sludge. This research study investigates the migration and transformation rule of heavy metals during the hydrolysis process by measuring the content of exchangeables (F1), bound to carbonates (F2), bound to Fe-Mn oxides (F3), bound to organic matter (F4), and residuals (F5) under different periods of time undergoing hydrolysis. The results show that the hydrolysis process generally stabilized Cu, Zn, Mn, Ni, Pb, Cr, and As by transforming the unstable states into structurally stable states. Such transformations and stabilization were primarily caused by the changes in local metal ion environment and bonding structure, oxidation of sulfides, pyrolyzation of organic matter, and evaporation of resulting volatile materials. An X-ray diffractometry (XRD) of the residuals conducted after hydrolysis indicated that hydrolysis did have a significant influence on the transportation and transformation of heavy metals.

Synthesis and Characterization of Eco-friendly Composite: Poly(Ethylene Glycol)-Grafted Expanded Graphite/Polyaniline

In this paper, synthesis and characterization of poly(ethylene glycol)- grafted expanded graphite/polyaniline (PEG-grafted EG/PANi) as a novel ecofriendly composite material was reported. EG as substrate prepared from expandable graphite was firstly synthesized by in-situ polymerization at the presence of aniline (An) to obtain EG/PANi, and then graft polymerization with as-prepared PEG-grafted PANi (PEG-g-PANi) composite under no tough conditions. Structural characteristics of the products were evaluated by infrared spectrum (IR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis. The experimental results have shown that the product of PEGgrafted EG/PANi composite were synthesized by facile method.

Hybrid Monolith of Graphene/TEMPO-Oxidized Cellulose Nanofiber as Mechanically Robust, Highly Functional, and Recyclable Adsorbent of Methylene Blue Dye

Herein we demonstrate first report on fabrication, characterization, and adsorptive appraisal of graphene/cellulose nanofibers (GO/CNFs) monolith for methylene blue (MB) dye. Series of hybrid monolith (GO/CNFs) were assembled via urea assisted self-assembly method. Hybrid materials were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction patterns, Raman spectroscopy, elemental analysis, thermogravimetric curve analysis, specific surface area, surface charge density measurement, and compressional mechanical analysis. It was proposed that strong chemical interaction (mainly hydrogen bonding) was responsible for the formation of hybrid assembly. GO/CNFs monolith showed mechanically robust architecture with tunable pore structure and surface properties. GO/CNFs adsorbent could completely remove trace to moderate concentrations of MB dye and follow pseudo-second-order kinetics model. Adsorption isotherm behaviors were found in the following order: Langmuir isotherm > Freundlich isotherm > Temkin isotherm model. Maximum adsorption capacity of 227.27 mg g−1 was achieved which is much higher than reported graphene based monoliths and magnetic adsorbent. Incorporation of nanocellulose follows exponential relationship with dye uptake capacities. High surface charge density and specific surface area were main dye adsorptive mechanism. Regeneration and recycling efficiency was achieved up to four consecutive cycles with cost-effective recollection and zero recontamination of treated water.

Optimized Process for Efficiently Extraction Protein from Excess Activated Sludge by Alcalase Hydrolysis

In this paper, we developed the utilization of excess activated sludge (EAS) to extract protein. Firstly, activated sludge was hydrolyzed, using six different commercial proteolytic enzymes by the Kjeldahl method, at their optimal conditions respectively, and Alcalase was chosen as the ideal for further analysis. Secondly, important parameters on protein extraction efficiency(PEE) of EAS by hydrolysis were investigated. Experimental results have been shown that 52.5% of protein was extracted from EAS (accounting for 30.5% of initial dry sludge (DS) weight) and reducing the quality of activated sludge about 35% under optimum hydrolysis conditions. This novel technology is more environmentally friendly than the conventional sludge treatments.