Minghuan Wang

Selective adsorption and separation of organic dyes from aqueous solution on polydopamine microspheres.

Polydopamine (PDA) microspheres, synthesized by a facile oxidation polymerization route, were evaluated as a potential adsorbent for selective adsorption and separation of organic dyes. The adsorption processes towards nine water-soluble dyes (anionic dyes: methyl orange (MO), eosin-Y (EY), eosin-B (EB), acid chrome blue K (ACBK), neutral dye: neutral red (NR), and cationic dyes: rhodamine B (RhB), malachite green (MG), methylene blue (MB), safranine T (ST)) were thoroughly investigated. The adsorption selectivity of organic dyes onto PDA microspheres was successfully applied for the separation of dyes mixtures. Various influential factors such as solution pH, temperature, and contact time were employed to ascertain the optimal condition for adsorption of representative organic dyes including MB, MG and NR. The pseudo-first-order and pseudo-second-order kinetics models were used to fit the adsorption kinetics process. Five isothermal adsorption models (Langmuir, Dubnin-Radushkevich, Temkin, Freundlich and Harkins-Jura) were used to investigate the adsorption thermodynamics properties. The results showed that the PDA microspheres owned good selective adsorption ability towards cationic dyes. The adsorption kinetics process conformed to the pseudo-second-order kinetics model and the Langmuir isotherm model was more appropriate for tracing the adsorption behavior than other isotherm models. Thus, we can conclude PDA microspheres may be a high-efficiency selective adsorbent towards some cationic dyes.

Fabrication of poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) nanotubes decorated with Ag–Au bimetallic nanoparticles with enhanced catalytic activity for the reduction of 4-nitrophenol

Ag–Au bimetallic nanoparticles (NPs) are deposited on poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) (PZS) nanotubes by a facile and effective co-reduction method, wherein the PZS nanotubes with abundant hydroxyl groups have been prepared via an in situ template approach. Upon varying the feeding amounts of the Ag and Au precursors, the bimetallic compositions of the PZS nanotubes can be readily tuned resulting in a series of bimetallic catalysts with different Ag to Au molar ratios, thus leading to the tunable catalytic properties. Characterization results show that the Ag–Au bimetallic nanoparticles with smaller size and good dispersibility are well anchored onto the surface of the PZS nanotubes. Furthermore, the reduction of 4-nitrophenol (4-NP) into 4-aminophenol (4-AP) by NaBH4 is applied as a model reaction to study the effect of different Ag-to-Au molar ratios on the catalytic capabilities of the resulting composites. It is found that the catalytic capability is remarkably enhanced when the Au content is increased. The maximum activity parameter value reaches 92.2 s−1 g−1, which is far higher than that of PZS nanotubes decorated with either Ag or Au nanoparticles alone.

Removal of Rhodamine B, a Cationic Dye From Aqueous Solution Using Poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) Nanotubes

Poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) (PZS) nanotubes were evaluated as an efficient adsorbent for the removal of Rhodamine B (RhB), a cationic dye from aqueous solution. The as-synthesized adsorbent (PZS nanotubes) were characterized by scanning electron microscopy (SEM), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR) and N2 adsorption/desorption isotherms. The factors influencing the adsorption efficiency and capacity had been systematically studied. Results showed that the adsorption was highly dependent on temperature, initial RhB concentration and adsorbent dose. Effects of initial solution pH indicate that the adsorption can proceed in both basic and acidic environment. The equilibrium absorption capacity at 25°C can reach up to 35.58 mg/g within 60 min implying the adsorption procedure was highly rapid. The kinetic data was better described by the pseudo-second-order model with the correlation coefficient (R2 = 0.9981), and the adsorption process followed Webers intraparticle model, indicating the adsorption process could be divided into two stages. Results also showed that the adsorption equilibrium obeyed the Langmuir isotherm, and the value of equilibrium parameter RL suggested that the PZS nanotubes were an efficient adsorbent for the removal of RhB from aqueous solution.

Novel N-doped porous carbon microspheres containing oxygen and phosphorus for CO2 absorbent and metal-free electrocatalysts

Novel N-doped porous carbon microspheres were synthesized facilely from polyphosphazene. These carbons exhibit a considerable performance for CO2 capture with high uptake, excellent selectivity, and good recyclability, and also show good electrocatalytic activity for oxygen reduction reaction.

A self-template and self-activation co-coupling green strategy to synthesize high surface area ternary-doped hollow carbon microspheres for high performance supercapacitors

Development of facile and cost-effective routes to achieve hierarchical porous and heteroatoms-doped carbon architectures is urgently needed for high-performance supercapacitor application. In our study, ternary-doped (nitrogen, phosphorus and oxygen) hollow carbon microspheres (NPO-HCSs) are fabricated by one-step pyrolysis of single poly(cyclotriphosphazene-co-phloroglucinol) (PCPP) microsphere, which is generated through a facile polymerization between hexachlorocyclotriphosphazene and phloroglucinol at mild conditions. The whole preparation process is not used any additional template or activating agent. The obtained NPO-HCS-950 with average diameter of 580 nm and shell thickness of about 80 nm have a high specific surface area (2390 m2 g-1), a large pore volume (1.35 cm3 g-1), hierarchically interconnected pore texture, and uniform ternary heteroatom doping (O: 3.04 at%; N: 1.33 at% and P: 0.67 at%). As an electrode material for supercapacitors, the specific capacitance of the NPO-HCS-950 reaches 253 F g-1 of 1 A g-1 and 176 F g-1 at 20 A g-1, revealing superior rate performance. The capacity retention after 10,000 consecutive charge-discharge cycles at 20 A g-1 is up to 98.9%, demonstrating excellent cycling stability. Moreover, the assembled symmetric supercapacitor using NPO-HCS-950 exhibits a relatively high energy density of 17.6 W h kg-1 at a power density of 800 W kg-1. Thus, a promising electrode material for high-performance supercapacitors is obtained through a facile, green and scalable synthesis route.