Immobilization of nanoscale Fe0 in and on PVA microspheres for nitrobenzene reduction.

In this study, nanoscale Fe(0) was immobilized in and on poly(vinyl alcohol) (PVA) microspheres by the inverse suspension crosslinked method. Two different sizes of Fe(0)/PVA microspheres were synthesized in the presence and absence of dispersant. The chelating action between Fe(2+) and PVA was identified by Fourier transform infrared and X-ray photoelectron spectroscopy. The morphology and distribution of the obtained Fe(0)/PVA microspheres were characterized by environmental scanning electron microscope, energy-dispersive X-ray spectrometry, and X-ray diffraction. Nanoscale Fe(0) particles were mostly dispersed over the surface of the microspheres. They were distributed more homogeneously on the surfaces of Fe(0)/PVA microspheres with diameter of 600-700 microm than those with diameter of 10-12 microm. The nitrobenzene (NB) reduction reactions followed pseudo-first-order kinetics. The normalized surface rate constants (k(SA)) values were determined to be 0.162 L h(-1)m(-2) for L-Fe(0)/PVA microspheres, 0.098 L h(-1)m(-2) for S-Fe(0)/PVA microspheres, and 0.023 L h(-1)m(-2) for nanoscale Fe(0) particles. Furthermore, with the analysis of the products by GC/MS, possible reductive pathways of NB by Fe(0)/PVA microspheres were suggested. The recovery rates of iron in microspheres were determined to be 81.17% for large Fe(0)/PVA and 60.31% for small Fe(0)/PVA.

[Effect of temperature on the Pb2+ biosorption with aerobic granules].

Experimental studies were conducted on the effect of temperature on the Pb2+ biosorption with aerobic granules seeding with floccular activated sludge. The results showed that the aerobic granules manly comprised the elements of C, H, N, O and P. According to the elemental compositions of the microbial granules, the corresponding empirical formula of the granules can be determined as C5.7 H10.9 O3.9 NS0.04. ESEM results showed many coccoid bacteria were visiable on the granule surface with porous structure. Both Freundlich and Langmuir isotherm equations could describe the biosorption process well (R2 > 0.914)under various temperature (20-40 degrees C). The maximum biosorption capacity (Q(max)) increased from 80.65 mg x g(-1) (20 degrees C) to 97.09 mg x g(-1) (40 degrees C). The values of thermodynamic parameters (deltaG < 0, deltaH > 0, deltaS > 0) indicated the biosorption process was spontaneous and endothermic in nature. Moreover, the Fourier transform infrared spectroscopy (FTIR) results demonstrated that such active groups as -OH, -COOH and P = O were involved in Pb2+ biosorption but nothing to do with nitrogen-containing groups.

[The development of the preamplifier for the microcomputer-detecting system of 3-channel ECG signals].

This paper introduces the preamplifier for the microcomputer-detecting system of 3-Channel ECG signals and its technical specifications. The practical experiments and clinical applications show that its performances conforms with all the requirements of the system.