Yijiu Li

Chromium adsorption on high-performance activated carbons from aqueous solution

The adsorption of Cr(VI) from aqueous solutions by commercial and lab-made high surface area (HSA)-activated carbons was investigated. Physiochemical factors such as equilibrium time, temperature and solution pH that affect the magnitude of Cr(VI) adsorption were studied. The HSA-activated carbons showed high performance for Cr removal, and their adsorption capacity is several times larger than that of commercial carbons. Both micropores and mesopores have important contribution on the adsorption. However, desorption is more dependent on the mesoporosity of activated carbons. Therefore, regeneration is easier for the carbon with high mesoporosity. As a result, the adsorption capacity of mesoporous carbon could be recovered over 97%, whereas 54% for highly microporous carbon.

Study on the treatment of copper-electroplating wastewater by chemical trapping and flocculation

Sodium diethyldithiocarbamate (DDTC) is used as a trapping agent and poly-ferric sulphate and polyacrylamide are used as flocculants to treat copper-electroplating wastewater. The influences on the precipitation and flocculation of Cu2+ cation are studied in details, such as the amount of complex copper (EDTA and NH4Cl are used as coordination agents), the addition of DDTC, poly-ferric sulphate and polyacrylamide (PAM) and pH of the solution. In addition, the influences on the trapping copper by different agents such as DDTC, diethylammonium diethyldithiocarbamate (DDC) and ammonium pyrrolidinedithiocarbamate (APDC) are studied as well. The results show that the dosage of DDTC depends only on the content of complex copper, but not on the total amount of copper in the wastewater. When the molar ratio of DDTC to Cu is between 0.8 and 1.2, Cu removal efficiency could be higher than 99.6%. Poly-ferric sulphate and PAM have little effects on the Cu removal, but they have significant effects on the flocculating volume, precipitation rate and nephelometric of the upper clean water.

Aniline degradation by electrocatalytic oxidation

The degradation of aniline solution in alkaline medium of pH 11.0 by electrocatalytic oxidation has been studied using an electrochemical reactor containing a SnO(2)-Sb(2)O(3)-PtO anode and a Ti cathode, both of 54 cm(2) area. Hydroxyl radicals (HO(z.rad;)) are produced at the anode, being tested with the trace catcher salicylic acid and phenol by spectrophotometery and high performance liquid chromatography. Intermediates dianiline, 4-anilino phenol and azobenzol were detected by gas chromatography-mass spectrometry. The existence of HO(z.rad;) produced in the aniline degradation was assayed with scavenger tertiary butanol. The results showed that electrocatalytic oxidation is an effective process for the degradation of aniline. A general reaction pathway that accounts for aniline degradation to CO(2) involving those intermediates is proposed.

The voltammetry-photocurrent response study of passivation of carbon steel in slightly alkaline solutions containing the corrosion inhibitor phosphor-polymaleic acid-ZnSO4

Abstract The electro-oxidation/electro-reduction processes on the surface of a carbon steel electrode were studied in borate buffer solutions (pH=8.4) in the presence and absence of the corrosion inhibitor phosphor-polymaleic acid (PPMA)–ZnSO 4 at room temperature by using the voltammetry–photocurrent response method. For the carbon steel electrode in solutions containing the corrosion inhibitor, its voltammograms displayed a smaller oxidation peak current and a larger photocurrent response compared to those in the reference solution. Further Auger electron spectroscopy (AES) analysis indicated that the passive films formed on the electrode consisted of ferric oxides and precipitation containing the corrosion inhibitor, which effect through blocking the metal surface, thereby, preventing the metal from further corrosion or dissolution.