No abstract

The synthesis of dimethyl carbonate (DMC) from urea and methanol was investigated, to explore the catalysts and reaction conditions. Among the catalysts, ZnO showed the highest catalytic activity toward DMC synthesis. Based on the experimental investigation, the reaction conditions over ZnO for a batch process were optimized, and the highest DMC yield attained (based on urea) was ∼30%, because of the presence of side reactions. In addition, the reusability test indicated that ZnO had high stability.

An ultrahigh molecular weight polyethylene (UHMWPE) fibrous adsorbent with amidoxime (AO) groups, denoted as AO-UHMWPE, was prepared by preirradiation-induced graft copolymerization of acrylonitrile (AN) and acrylic acid (AA) on UHMWPE fibers, followed by amidoximation. The chemical structure, thermal stability, and mechanical strength were evaluated by means of Fourier transform infrared spectrometry, thermogravimetric analysis, and tensile tests, respectively. The adsorption behaviors of the AO-UHMWPE fiber were studied by batch adsorption in 331 ppb uranium solution, and flow-though adsorption experiments in simulated and natural seawater. It was found that the adsorption conditions (i.e., contact time and manner, temperature, and uranyl ion initial concentration) significantly influence the amount of uranyl ions binding to the AO-UHMWPE fibers. The adsorption of uranium in the batch adsorption experiment was 4.54 g-U/kg-ad in the presence of massive amounts of interference ions.