Effective adsorption of sulfate ions with poly(m-phenylenediamine) in aqueous solution and its adsorption mechanism

Sulfate adsorption by poly（m-phenylenediamine）s（PmPDs） with various oxidation states synthesized through chemically oxidative polymerization was investigated.Series of sorption experiments were conducted,and the adsorption mechanism and the relationship between oxidation state and adsorption performance were studied with the characterization of Fourier transform infrared spectroscopy（FTIR）,X-ray photoelectron spectroscopy（XPS）,pH tracking and energy calculation.The results show that the adsorption performance in acidic solution is improved with the decrease of oxidation state of poly（m-phenylenediamine）（PmPD）.The rate constant is as high as 425.5 mg/（g·min） in the short equilibrium time of 30 min.The estimated highest adsorptivity of sulfate ions is 95.1%.According to the Langmuir equation,the adsorbance is 108.5 mg/g.The sulfate desorption efficiency is about 95% and the accumulative adsorbance is up to 487.95 mg/g in 5 cycles.

重庆地区云水的飞机观测

1989年10月3～13日,在重庆地区上空1500～4000m 进行了云水和污染气体的飞机观测。结果表明云水大都酸化并污染,亚硫酸根在硫氧酸根中占33.5％。

Ozonation of Sulfur Dioxide in Sulphuric Acid Solution

In this study, the oxidation rates of sulfur dioxide （SO2） in sulphuric acid solution by ozone and oxygen were compared, and the oxidation mechanism of ozone on SO2 was investigated. The results showed that the oxidation-reduction potential of the acidic solution was enhanced, the transformation rate of sulfuric acid to sulphuric acid was increased and the absorption driving force was improved in the presence of ozone. By comparing the amount of sulfate ions measured in the experiments and the theoretical amount of sulfate ions calculated from the amount of ozone consumed in the reaction, it can be confirmed that oxygen free radicals from dissociation of ozone are reactive as an efficient oxidant and oxygen from ozone generator participates in the reaction with SO2. 0.602 mol of effective oxygen was introduced into the reaction by one mole of ozone in 10.15 rain at sulphuric acid concentration of 3% （by mass）, SO2 concentration of 1.33% （by volume） and oxygen flow rate of 1.5 L.min^-1 from ozone generator.

Preparation and Acid Catalytic Activity of TiO2 Grafted Silica MCM-41 with Sulfate Treatment

TiO2 grafted silica MCM-41 catalyst with and without sulfate treatment were prepared. The structural and acid properties of these materials were investigated by XRD, N2 adsorption-desorption, element analysis, thermal analysis, Raman and FTIR measurements. Their acid-catalytic activities were evaluated using the cyclization reaction of pseudoionone. It was found that the obtained materials possess well-ordered mesostructure, and the grafted TiO2 components were in highly dispersed amorphous form. T/MCM41 without sulfation contained only Lewis acid sites, while Brφnsted and Lewis acidities were remarkably improved for the sulfated materials ST/MCM41 and d-ST/MCM41. T/MCM-41 was not active for the cyclization reaction of pseudoionone, but ST/MCM-41 and d-ST/MCM-41 possessed favorable catalytic activities. The catalytic performance of ST/MCM-41 was comparable with that of the commercial solid acid catalyst of Amberlyst-15, and better than that of d-ST/MCM-41, although the latter underwent a second TiO2 grafting process and accordingly had higher Ti and S content. The specific surface structure of Si-O-Ti-O-S=O in ST/MCM-41 and the bilateral induction effect of Si and S=O on Si-O-Ti bonds were speculated to account for its higher acid catalytic activity.

Effect of Sulfate Adlayer on Formic Acid Oxidation on Pd(111) Electrode

The kinetics of formic acid oxidation (FAO) on Pd(111) in 0.1 mol/L H2SO4+0.1 mol/L HCOOH with and without addition of Na2SO4 is studied using cyclic voltammetry and potential step method, which is compared with that in 0.1 mol/L HClO4. It is found that adsorbed sulfate has significant inhibition effect on FAO kinetics. After addition of 0.05 mol/L or 0.1 mol/L Na2SO4, FAO current in the negative-going scan is found to be significantly smaller than that at the same potential in the positive-going scan. We speculate that at potentials positive of the phase transition potential for the (SO4*ad)m+[(H2O)n-H3O+] or(SO4*ad)m+[Na+(H2O)n-H3O+] adlayer, the adlayer structure probably becomes denser and more stable with the increase of potential or with the addition of Na2SO4. The formation of connected adlayer network greatly enhance the stability of the adlayer, and the insertion of positive-charged H+ or Na+ into the adlayer network further reduces the electrostatic repulsion between partially charged sulfates. As a result, the destruction/desorption of compact sulfate adlayer becomes more difficult, which leaves much less free sites on the surface for FAO, and thus FAO kinetics at higher potentials and in the subsequent negative-going potential scan is significantly inhibited.

Anomalous self-optimization of sulfate ions for boosted oxygen evolution reaction

Broadly,the oxygen evolution reaction(OER)has been deeply understood as a significant part of energy conversion and storage.Nevertheless,the anions in the OER catalysts have been neglected for various reasons such as inactive sites,dissolution,and oxidation,amongst others.Herein,we applied a model catalyst s-Ni(OH)2 to track the anionic behavior in the catalyst during the electrochemical process to fill this gap.The advanced operando synchrotron radiation Fourier transform infrared(SR-FTIR)spectroscopy,synchrotron radiation photoelectron spectroscopy(SRPES)depth detection and differential X-ray absorption fine structure(D-XAFS)spectrum jointly point out that some oxidized sulfur species(SO_(4)^(2-))will selfoptimize new Ni–S bonds during OER process.Such amazing anionic self-optimization(ASO)behavior has never been observed in the OER process.Subsequently,the optimization-derived component shows a significantly improved electrocatalytic performance(activity,stability,etc.)compared to reference catalyst Ni(OH)_(2).Theoretical calculation further suggests that the ASO process indeed derives a thermodynamically stable structure of the OER catalyst,and then gives its superb catalytic performance by optimizing the thermodynamic and kinetic processes in the OER,respectively.This work demonstrates the vital role of anions in the electrochemical process,which will open up new perspectives for understanding OER and provide some new ideas in related fields(especially catalysis and chemistry).