The retention behaviour and separation of some water-soluble organophosphorus insecticides on polyester-based polyurethane foams.
This paper reports the concentration of some dissolved organic phosphorus insecticides in water by open-cell polyurethane foam. The results of preliminary screening tests on the retention of the tested insecticides (Diazinon, Malathion and Chloropyrifos) by polyester foams indicated that a very high percent removal of the insecticides was obtained. The retention rate was fast and reaches equilibrium in a few minutes. The various parameters affecting the preconcentration of the tested insecticides by unloaded foam, e.g. pH, extraction media, shaking time, salt effect, flow rate, temperature and sample volumes have been optimized via the static mode of separation. The unloaded foams were employed in columns for the retention and recovery of the tested species. The sorption efficiency and the recovery of the tested compounds by the unloaded foam column were found to be up to 95.5%. The equivalent to a theoretical plate by the unloaded foam was found in the range 1.12 - 1.32 +/- 0.2 mm. The sorption mechanism of the tested species by the foam is discussed. The separation of some of the tested species in a mixture was achieved. The foam membrane offers unique advantages over conventional bulk-type granular sorbents and solvent extraction in offering high flow rates, rapid, versatile, effective separation and preconcentration of different species from aqueous samples. The foam provides the advantages of being, insoluble, easily separable and non-polluting, as well as inexpensive.
Distribution of organophosphate insecticides in a Thai biomass-water system
Sorption and leaching of the organophosphate (OP) pesticides chlorpyrifos, profenofos, methyl parathion and malathion were investigated with four different types of biomass: coconut husk, rice husk, peat moss and peanut shell. Organic carbon contents of the biomass were in the range of 35.4–45.4%. Sorption studies were carried out by the batch (equilibrium) method at 4 different OP spike concentrations and at pH 3–7. Sorption isotherms conformed to a linear Freundlich equation and the Freundlich constant or sorption coefficient (KD) confirmed that biomass organic carbon content was the principal sorbent factor affecting OP sorption. For a given sorbent, correlation of the extent of sorption with sorbate chemical properties was examined. Column leaching experiments involving different masses of coconut husk and peanut shell pre-spiked with OPs at the level equivalent to actual spraying concentrations in some Thai tangerine orchards were conducted. These experiments included repeated spikings and leaching. A water flow rate of 20 mL min−1 was employed corresponding to the current average watering regime. Retardation and biodegradation with these sorbents were also examined.
Badush Dam, NW Iraq : A Geological Study
The river Tigris flows from Turkey towards Iraq in its northwestern part dissecting the whole Iraqi territory. During 1981– 1986 a very large earth fill dam was constructed, which is Mosul Dam impounding the flow of the Tigris River. It is the largest dam in Iraq and one of the largest in the Middle East. The geological conditions of the dam site and surroundings, however, are not suitable due to thick exposures of the Fatha Formation, which consists of marl, clay, limestone and gypsum. The gypsum and limestone beds are highly karstified causing severe problems to the dam foundation. Mosul dam suffers from serious problems due to the presence of karstified rocks; therefore, the Ministry of Irrigation in Baghdad, decided to construct a protection dam downstream of Mosul Dam; it is called Badush Dam. The geological conditions at Badush Dam site are the same as those at Mosul Dam site, which means the foundations of the dam are located on karstified rocks. Therefore, grouting works were planned and designed and it was partly performed from the beginning of the construction in 1988. The construction of the dam; however, stopped in 1991 due to the consequences of the First Gulf War. The constructed parts of the dam are (30 – 40) %. In this study, we have presented the main problems, which will cause real danger to Badush Dam, if its construction is re-started, and we have suggested many requirements to avoid any hazard that may cause the collapse of Badush Dam.