Removal of total cyanide in coking wastewater during a coagulation process: Significance of organic polymers

Whether a cationic organic polymer can remove more total cyanide （TCN） than a non-ionic organic polymer during the same flocculation system has not been reported previously. In this study, the effects of organic polymers with different charge density on the removal mechanisms of TCN in coking wastewater are investigated by polyferric sulfate （PFS） with a cationic organic polymer （PFS-C） or a non-ionic polymer （PFS-N）. The coagulation experiments results show that residual concentrations of TCN （Fe（CN）6^3-） after PFS-C flocculation （TCN 〈 0.2 mg/L） are much lower than that after PFS-N precipitation. This can be attributed to the different TCN removal mechanisms of the individual organic polymers. To investigate the roles of organic polymers, physical and structural characteristics of the floes are analyzed by FT-IR, XPS, TEM and XRD. Owing to the presence of N＋ in PFS-C, Fe（CN）3- and negative flocs （Fe（CN）63- adsorbed on ferric hydroxides） can be removed via charge neutralization and electrostatic patch flocculation by the cationic organic polymer. However, non-ionic N in PFS-N barely reacts with cyanides through sweeping or bridging, which indicates that the non-ionic polymer has little influence on TCN removal.

Phytochemical Study and Anti-nutritional Factors in Stems of Dioscorea praehensilis Benth(Dioscoreaceae)

The aim of this research was to find and assay phytochemical compounds and various biological macromolecules of the tender stems of Dioscorea praehensilis benth and evaluate their antioxidant activity and to compare the content of oxalates and cyanogenetic glucosides between raw and cooked tender stems.The plant collection and identification,phytochemical evaluation:phytochemical screening,preliminary(qualitative)analyses and in vitro assays.Phytochemical screening was performed by qualitative methods.The estimation of the content of secondary metabolites was evaluated by spectrophotometry-UV.Antioxidant activity was evaluated using the ABTS and DPPH assays and preliminary composition by the gravimetric method.The results obtained show that the stems of Dioscorea praehensilis are devoid of certain important chemical groups,the flavonoids were not detected and they were rich in total polyphenols(17.22±0.16),tannins(19.32±0.52)and anthocyanins(25.22±0.04).Our extracts showed a lower antioxidant activity than that of positive controls.The samples are rich in carbohydrates and fiber,with low levels of proteins,lipids and ash.Dioscorea praehensilis has a high toxicity in HCN,but after a good cooking of about 1 hour,99.97%of the cyanide are eliminated and does not have many oxalates.The results obtained show that Dioscorea praehensilis has a high dietary value and can therefore be used as a nutritive food.