Purification,characterization and application of dual coagulants containing chitosan and different Al species in coagulation and ultrafiltration process

The objective of this study was to investigate the effect of different Al species and chitosan（CS） dosages on coagulation performance,floc characteristics（floc sizes,strength and regrowth ability and fractal dimension） and membrane resistance in a coagulation-ultrafiltration hybrid process.Results showed that different Al species combined with humic acid in diverse ways.A1_a had better removal efficiency,as determined by UV_（254） and dissolved organic carbon,which could be further improved by the addition of CS.In addition,the optimal dosage of different Al species was determined to be 4.0 mg/L with the CS concentration of 1.0 mg/L,by orthogonal coagulation experiments.Combining Al_a/A1_b/A1_c,with CS resulted in larger flocs,higher recovery,and higher fractal dimension values corresponding to denser flocs;in particular,the floc size at the steady state stage was four times larger than that obtained with Al species coagulants alone.The results of ultrafiltration experiments indicated that the external fouling percentage was significantly higher than that of internal fouling,at around 85%and 15%,respectively.In addition,the total membrane resistance was significantly decreased due to CS addition.

Species analysis methods for hydrolysis polymerization of aluminum

Al Ferron timed complex colorimetric method (AFM) and 27 Al NMR spectroscopy method(ANM) were discussed. For the former, the different colorimetric reagent preparation methods' results indicate that there are some differences beteween them, and the combined method can be used as a simplified procedure. For the latter, the small tube method is more accurate. Eventually, the Al 13 (ANM) was compared to the Al b (AFM).

Preparation of high concentration polyaluminum chloride with high content of Al_b or Al_c

A novel membrane distillation concentration method was used m prepare high concentration polyaluminum chloride （PAC1） with high content of AID or Ale. 2.52 mol/L PACl1 with 88% Alb and 2.38 mol/L PACl2 with 61% Ale were successfully prepared. Three coagulants, AlCl3, PACl1 and PACl2 were investigated on their hydrolysis behavior and speciation under different conditions. The effects of pH and dilution ratio on Al species distribution were investigated by ferron assay. Experimental result showed that pH had a significant effect on Al species distribution for the three coagulants. Dilution ratio had little effects on Alb and Alc distribution in whole dilution process except the beginning for PACl1 and PACl2. The results indicated that transformation of Al depends largely on their original composition. AlCl3 was the most unstable coagulant among these three coagulants during hydrolysis process. PACl1 and PACl2 with significant amounts of highly charged and stable polynuclear aluminum hydrolysis products were less affected by the hydrolysis conditions and could maintain high speciation stability under various conditions.

Spectroscopic study on variations in illite surface properties after acid-base titration

FT IR, Raman microscopy, XRD, 29 Si and 27 Al MAS NMR, were used to investigate changes in surface properties of a natural illite sample after acid base potentiometric titration. The characteristic XRD lines indicated the presence of surface Al Si complexes, preferable to Al(OH) 3 precipitates. In the microscopic Raman spectra, the vibration peaks of Si O and Al O bonds diminished as a result of treatment with acid, then increased after hydroxide back titration. The varied ratio of signal intensity between IV Al and VI Al species in 27 Al MAS NMR spectra, together with the stable BET surface area after acidimetric titration, suggested that edge faces and basal planes in the layer structure of illite participated in dissolution of structural components. The combined spectroscopic evidence demonstrated that the reactions between illite surfaces and acid leaching silicic acid and aluminum ions should be considered in the model description of surface acid base properties of the aqueous illite.

Preface to the SPECI AL ISSUE: Excitonic Solar Cells(Ⅰ)

Search and development of clean sustainable energy or renewable energy become an imperative demand beyond the concerns of limited resource and cost of fossil fuels that our modern life is so much dependent on.Among all the renewable energy,solar energy is the most abundant and likely to make the most significant contribution to the clean energy efforts.Although the usage of solar energy has