No abstract

The role of solution composition and ageing of arsenite treated with single and mixed mineral systems of kaolinite, montmorillonite and goethite injected with iron sulfide under sulfidic-anoxic conditions have been investigate. Variability in arsenite sorption exists over the range of pH investigated. This variability in sorption may be attributed to the presence of thiol (≡S-H) functional group contained in solution under sulfidic-anoxic condition. Arsenite sorption exhibits a non-promotive Cp effect (i.e. sorption decreases as Cp increases for all mineral systems. the nature of ionic species formed in solution is affected by changes in the mineral/ solution ratio. All mineral systems but kaolinite-goethite exhibits a step up arsenite sorption up to 288 hours residence time and flattens g out over the remaining residence time of the reactions.

Abstract:Mineral systems of kaolinite, montmorillonite, goethite and their mixtures were investigated to determine their effect on arsenite removal. Experimental studies include characterization and batch mode experiments. This study was in relation to solution composition and ageing relevant to streams and groundwater impacted by arsenic. Sorption isotherms indicated that sorption capacities of the different clay minerals, goethite and their mixtures were dependent on particle size, pH, particle concentration, arsenic concentration and residence time. Batch mode studies at room temperature revealed increase in sorption as pH was increased. All mineral systems exhibited increase in sorption as initial arsenic concentration increased. All mineral systems exhibited both promotive and non-promotive Cp effects. The complex behavior of mineral systems over the range of residence time investigated may be attributed to increased hydroxylation of the mineral surface and availability of thiol (≡S-H) and hydroxyl (≡Me-OH) functional groups and reactive sites.

No abstract

No abstract

No abstract

Sorption of Cu and Zn was investigated using single and mixed mineral systems under sulfidic-anoxic condition to treat wastewater obtained from disused mine pits at Parys Mountain in, United Kingdom. Water courses are the recipients of these contaminants. In these water courses fishing activities exist. Attempt was made to reduce the Cu and Zn levels intake in the watercourses using mineral systems of clays and goethite. These were tested with the mine waste water for characterization of copper and zinc removal at variable pH, solid concentration and contact time. In addition, levels of saturation of hydroxyl complexes were modeled. Batch reactions conducted at ambient temperature (23±2°C) reveal all systems of assorted minerals sorbed more Cu than Zn. In addition, Cu sorbed on iron sulfide exhibited increase in sorption with increasing pH. There was cross cutting effect of Cu and Zn sorbed on iron sulfide at pH 6 and Cu sorbed on goethite at about pH 7, These indicate similar metal removal characteristics. Differences in removal of copper and zinc ions may be assigned to outer sphere complexation and specific adsorption of copper and zinc ions. Non-promotive Cp effect (i.e. decrease in metal removal with increase in concentration of particle) was observed in all minerals. This effect may be assigned to increase in aggregation of the mineral particle size. Ageing characterization progresses as residence time was increased. This may be assigned thiol (=S-H) and hydroxyl (=Me-OH) groups and sites of reactions. There is no link to stable hydroxylation of copper and zinc species that could significantly contribute to the removal of these metals.

No abstract