Wenqi Gong

A real time in situ ATR-FTIR spectroscopic study of linear phosphate adsorption on titania surfaces

Abstract A real time in situ attenuated total reflection Fourier transform infrared (ATR-FTIR) technique was developed to study the adsorption of linear phosphates with different number of P atoms on titania surface from aqueous solutions. The species adsorbed on titania surface from orthophosphate solution in a wide pH range were identified as two kinds of species. One is a bridging bidentate surface complex (TiO)2PO2 with C2v symmetry, the other is an electrostatically adsorbed ion with Td symmetry. The linear polyphosphate species interact through the P–O groups with the titanium ions exposed on titania surface to form P–O–Ti bond and adsorb in a “flat” conformation on the surface. Significant change of the adsorbed phosphate species on titania surface during the initial few minutes of the adsorption process has been detected by the real time in situ ATR-FTIR spectroscopic technique. The polyphosphate species displace the monomeric species adsorbed earlier and become dominant on titania surface. The chemisorption of the phosphate species attains equilibrium faster than the physical adsorption of the phosphate species. The adsorption of phosphate species attains equilibrium faster in solution of higher concentration. The adsorption of polymeric phosphate species attains equilibrium at a lower speed than the monomers.

Removal of Neutral Red from aqueous solution by adsorption on spent cottonseed hull substrate

Cottonseed hull, a low-cost widely available agricultural waste in China, after used as substrate for the white rot fungus Pleurotus ostreatus cultivation, was tested for the removal of Neutral Red (NR), a cationic dye, from aqueous solution. A batch adsorption study was carried out with varied solution pH, adsorbent dosage, reaction time and initial NR concentration. The results show that the kinetics of dye removal by the spent cottonseed hull substrate (SCHS) is prompt in the first 5 min and the adsorption equilibrium can be attained after 240 min. The biosorption kinetics and equilibrium follow typical pseudo-second-order and Langmuir adsorption models. Thermodynamic parameters of ΔG°, ΔH° and ΔS° show that the adsorption is a spontaneous and endothermic process. Fourier transform infrared (FTIR) spectroscopy was used for the characterization of possible dye-biosorbent interaction. This study provides a facile method to produce low-cost biosorbent for the purification of dye contaminated water.

Anaerobic biodegradation of ethylthionocarbamate by the mixed bacteria under various electron acceptor conditions.

Biodegradation behavior and kinetics of ethylthionocarbamate under nitrate, sulfate and ferric reducing conditions by mixed cultures enriched from the anaerobic digester sludge was investigated. The results showed that ethylthionocarbamate could be degraded independently by the mixed cultures coupled to nitrate, sulfate, and ferric reduction, and meanwhile, nitrite, sulfide, and ferrous were accumulated as a result of nitrate, sulfate and ferric reduction, respectively. Ferric was a more favorable terminal electron acceptor compared to nitrate and sulfate. The order of the electron acceptors with decreasing biodegradation rates of the ethylthionocarbamate was: ferric>nitrate>sulfate, and the corresponding maximum biodegradation rate was 7.240, 6.267, and 4.602 mg/(L·d), respectively. The anaerobic biodegradation of ethylthionocarbamate under various electron acceptor conditions can be accurately described by first order exponential decay kinetics.

Integrated assessment for aerobic biodegradability of sulfide mineral flotation collectors

ABSTRACT The biodegradability of flotation collectors has the most important impact on mine environment. Understanding the flotation collectors’ biodegradability is a crucial element in developing an informed strategy for analysing and managing the mine environment. Integrated assessment method including three biodegradability tests namely, BOD5/CODCr ratio test, Static-flasks test and OECD 301B have been established to evaluate the aerobic biodegradability of the sulfide mineral flotation collectors. Consistent conclusions have been obtained through these three biodegradability tests: the aerobic biodegradation of the different sulfide mineral flotation collectors is different, namely, sodium diethyldithiocarbamate is a readily biodegradable collector, and ammonium butyl-dithiophosphate is partially biodegradable. However, n-butyl xanthate and ethylthionocarbamate are considered as poorly biodegradable. Besides, the order of aerobic biodegradability of these collectors is: sodium diethyldithiocarbamate >...