硫酸根对甲基磺酸体系镀锡液性能的影响

目的从镀层的耐蚀性能、电化学行为、镀液稳定性三个层面分析硫酸根对甲基磺酸体系镀锡的影响,探究在不影响镀液性能的条件下,硫酸根在甲基磺酸镀锡液中的最大浓度范围。方法通过盐雾实验和电化学测试探究硫酸根对镀锡板耐蚀性能的影响,通过电化学测试研究了硫酸根在甲基磺酸镀锡过程中的电化学行为,通过可见光分光光度计和zeta电位仪分析硫酸根对镀液稳定性的影响。结果镀液中硫酸根质量浓度在5 g/L时,镀层的耐蚀性能最好,但硫酸根质量浓度高于10 g/L时,镀层耐蚀性呈下降趋势。在锡沉积过程中,硫酸根离子的存在会增大锡沉积的阴极极化,当镀液中的硫酸根质量浓度达到60g/L时,阴极极化不再显著增加。透过率随时间变化的曲线表明,当MSA和甲基磺酸混合溶液中不存在硫酸根时,溶液的氧化速度较慢,溶液透光率经过196 h后由99%下降为86%。硫酸根的加入会使镀液的氧化速率加快,当溶液中硫酸根质量浓度分别为20、40、60、80 g/L时,196 h后,透光率分别下降至15%、66%、63%、20%。硫酸根的加入,也会改变溶液的zeta电位,使胶粒由荷正电变为荷负电。结论当镀液中硫酸根质量浓度超过10g/L时,镀锡层的耐蚀性能下降。硫酸根能够增大锡沉积的阴极极化,加速锡离子的氧化;此外,硫酸根还会吸附在锡胶粒表面,使添加剂浊点降低。

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.

Unravelling Hydrogen Adsorption Kinetics on Ir(111)Electrode in Acid Solutions by Impedance Spectroscopy

The kinetics for hydrogen(H)adsorption on Ir(111)electrode has been studied in both HClO_(4) and H_(2)SO_(4) solutions by impedance spectroscopy.In HClO_(4),the adsorption rate for H adsorption on Ir(111)increases from 1.74×10^(-8)mol·cm^(-2)·s^(-1) to 3.47×10^(-7)mol·cm^(-2)·s^(-1) with the decrease of the applied potential from 0.2 V to 0.1 V(vs.RHE),which is ca.one to two orders of magnitude slower than that on Pt(111)under otherwise identical condition.This is explained by the stronger binding of water to Ir(111),which needs a higher barrier to reorient during the under potential deposition of H from hydronium within the hydrogen bonded water network.In H_(2)SO_(4),the adsorption potential is ca.200 mV negatively shifted,accompanied by a decrease of adsorption rate by up to one order of magnitude,which is explained by the hindrance of the strongly adsorbed sulfate/bisulfate on Ir(111).Our results demonstrate that under electrochemical environment,H adsorption is strongly affected by the accompanying displacement and reorientation of water molecules that initially stay close to the electrode surface.

Cu Secondary Adsorption by Some Variable Charge Soils After Adsorbing SO_4^(2-)

Cu secondary adsorption by three variable charge soils collected from hubei Province and Hunan Province was investigated.The amount of Cu secondary adsorption increased with that of SO4^2- elementary adsorption and conformed with the Langmuir,freundlich and Temkin isotherms.Desorption of secondary-adsorbed Cu indicated that the hysteresis ratio decreased as Cu secondary adsorption increased,which meant that secondry-adsorbed Cu existed not only in the exchangeable form but also in the bridge form and specifically adsorbed form.The amount of Cu secondary adsorption increased with the temperature.

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.