Preparation of polymer microspheres with reactive epoxy group and amino groups as stabilizers for gold nanocolloids with recoverable catalysis

Adsorption Behavior and Mechanism of Palladium on Diethylaminoethyl-Modified Polyglycidyl Methacrylate Macroporous Spheres

The recovery of precious metals, such as palladium (Pd), from wastewater, is an economically important field. The present study reports the application of polyglycidyl methacrylate (PGMA) macroporous spheres with diethylaminoethyl (DEAE) functional groups (PGMA-DEAE) for the adsorption of palladium ions [Pd(II)] from simulated wastewater solutions. The effects of pH, adsorption duration, and initial concentration of Pd(II) on the adsorption amount were evaluated systematically. The results revealed that within the experimental pH range, the adsorption efficiency of Pd(II) increased with increasing pH. In particular, between pH 4 and 6, the Pd(II) adsorption efficiencies were approximately 100%. At 298 K and pH ∼ 4, the adsorption capacity of PGMA-DEAE for Pd(II) was 1.22 mmol/g. The adsorption rates of PGMA-DEAE for Pd(II) were high, and the adsorption equilibrium was reached within 10 min. Ca(II), Mg(II), Co(II), Cu(II), Ni(II), and Fe(II) were selected as representative competitive adsorption metal ions. PGMA-DEAE had good separation selectivity for Pd(II) at pH 1-6 (all RPd/Me > 30), especially at pH ∼ 4 (all RPd/Me > 100). The SEM, TEM, EDS, TG, XRD, and XPS results indicated that in a high-acidity environment (CHCl ≥ 1 mol/L), Pd(II) was adsorbed on PGMA-DEAE through electrostatic attraction, while in a low-acidity environment (pH 1-6), Pd(II) was adsorbed on PGMA-DEAE through coordinated bonding between the Pd(II) ions and the N. PGMA-DEAE exhibited excellent stability and regeneration performance for five regeneration cycles.

Precipitation Polymerization: A Powerful Tool for Preparation of Uniform Polymer Particles

Precipitation polymerization (PP) is a powerful tool to prepare various types of uniform polymer particles owing to its outstanding advantages of easy operation and the absence of any surfactant. Several PP approaches have been developed up to now, including traditional thermo-induced precipitation polymerization (TRPP), distillation precipitation polymerization (DPP), reflux precipitation polymerization (RPP), photoinduced precipitation polymerization (PPP), solvothermal precipitation polymerization (SPP), controlled/‘‘living’’ radical precipitation polymerization (CRPP) and self-stabilized precipitation polymerization (2SPP). In this review, a general introduction to the categories, mechanisms, and applications of precipitation polymerization and the recent developments are presented, proving that PP has great potential to become one of the most attractive polymerization techniques in materials science and bio-medical areas.

AuNPs-Based Thermoresponsive Nanoreactor as an Efficient Catalyst for the Reduction of 4-Nitrophenol

A new AuNPs-based thermosensitive nanoreactor (SiO₂@PMBA@Au@PNIPAM) was designed and prepared by stabilizing AuNPs in the layer of poly(N,N'-methylenebisacrylamide) (PMBA) and subsequent wrapping with the temperature-sensitive poly(N-isopropylacrylamide) (PNIPAM) layer. The new nanoreactor exhibited high dispersibility and stability in aqueous solution and effectively prevented the aggregation of AuNPs caused by the phase transformation of PNIPAM. The XPS and ATR-FTIR results indicated that AuNPs could be well stabilized by PMBA due to the electron transfer between the N atoms of amide groups in the PMBA and Au atoms of AuNPs. The catalytic activity and thermoresponsive property of the new nanoreactor were invested by the reduction of the environmental pollutant, 4-nitrophenol (4-NP), with NaBH₄ as a reductant. It exhibited a higher catalytic activity at 20 °C and 30 °C (below LCST of PNIPAM), but an inhibited catalytic activity at 40 °C (above LCST of PNIPAM). The PNIPAM layer played a switching role in controlling the catalytic rate by altering the reaction temperature. In addition, this nanoreactor showed an easily recyclable property due to the existence of a silica core and also preserved a rather high catalytic efficiency after 16 times of recycling.