Date of Award
Master of Science (MS)
Dr. M . S. EI-Shahawi
Sherif H Kandil
ZAkaria M El Attal
Heavy metals and pesticides represent a class of man-made environmental pollutants which also occur naturally in the environment. The presence of these pollutants in the industrial and agricultural wastewaters often represents a risk to the environment. Investigation of these species in the water is an important aspect of environmental pollution as human activities contributed to the progressive increase in the concentration of these compounds in the environmental as well as aquatic systems. Therefore, identification and removal (or reduction) of these species to an acceptable concentration are of prime importance.
The analytical utility of unloaded open-cell polyurethane foams and foams immobilizing some chromogenic organic reagents (chromoforms) as cellular solid extractor, is considered as a useful addition to the field of separation science and preconcentration techniques. Polyurethane foam allows the isolation of the analyte from the matrix and yields an appropriate enrichment factor. The quasi-spherical membrane structure, the good hydrodynamic and the resilience properties of the foam offers real advantages over the well-known granular supports e.g. Voltaleff which is considered one of the excellent support in the literature in separation and preconcentration of trace amounts of organic and inorganic pollutants from different media.
In the present study polyether type polyurethane foam has been used as a trapping medium for the preconcentration and quantitative recovery of some pyrethroid and phosphorous insecticides (commonly in use by the Ministry of Agriculture and Fisheries of UAE) from high volume sample of agricultural waters. The detection and semiquantitative determination of bismuth (III) in aqueous acidic media by polyether foam employing 1, 5-di-(phenyl)-3-mercaptoformazan (H2Dz) and 1, 5-di (2-fluorophenyl)-3-mercaptoformazan (F2H2Dz) have been critically investigated.
Unloaded foams were employed in static and dynamic modes for the retention and separation behaviour of a series of pesticides e.g. Cypermethrin, Parathion, Malathion and Chloropyrifos in aqueous media. The effect of different parameters, e. g. contact time, extraction media, solution pH, insecticide concentration, temperature, salt effect and cation size of adding salts affecting the retention behaviour of each insecticide on unloaded foam was investigated. The sorption behavior of Parathion and Malathion in the presence of different univalent cation sizes increased in the order:
Li+ > Na+ > K+ > NH4+
In good agreement with the solvent extraction mechanism, while Cypermethrin and Chloropyrifos follow the sequence:
K+ > NH4+ > Na+ > Li+
Indicating sorption of these species by the "cation chelation mechanism". The thermodynamic parameter, e. g. ΔHo and ΔSo for the sorption process of the tested insecticides by the unloaded foams were obtained. The column performance, the critical capacity, the highest equivalent to the theoretical plates (HETP) and the number of the theoretical plates (N) were also calculated and discussed. Separation of some of the tested insecticides was also achieved.
Plant analysis of Tomato and Parsley plants untreated and sprayed with Chloropyrifos for different time intervals 24, 72 and 120 hrs. was carried out. The analysis of nitrogen, phosphorous, sodium, potassium, copper, zinc, manganese, iron, humidity, wet weight and dry weight of controlled and sprayed plants were achieved and discussed.
The qualitative and semiquantitative determination of bismuth (III) in aqueous acidic (pH < 5) employing the chromogenic reagents H2Dz and F2H2Dz- immobilized or plasticized tri-n-butylphosphate (TBP) loaded foams were achieved via batch, dynamic and pulsating column modes of extraction.
- i. In the batch extraction mode, the detection of 0. 02 ppm of bismuth (III) in aqueous acidic solution from a mixture containing the tested metal ion and F2H2Dz was achieved on unloaded foams. The detection of 0.01 and 0.005 ppm of bismuth (III) were also obtained with polyurethane foam treated with F2H2Dz and plasticized F2H2Dz-TBP foams, respectively. As low as 0.02 ppm of bismuth (III) were also detected on polyurethane foams loaded with H2Dz or plasticized H2Dz-TBP foams. The semiquantitiative determination of bismuth (III) in aqueous acidic solution employing polyurethane foam loaded and plasticized with H2Dz and F2H2Dz was successfully carried out.
- ii. In the flow (column) technique, the detection and semiquantitative determination of bismuth (III) ions were successfully achieved at the ng cm-3 (ppb) concentration level using immobilized and plasticized polyurethane foam with the reagents H2Dz and F2H2Dz. The length of the coloured zone was taken as a semiquantitative measure of metal ion concentrations.
- iii. Based on the resilient properties of the open-cell polyurethane foam it was possible to detect as low as 5 ppb of bismuth (III) in aqueous acidic solution by plasticized F2H2Dz-TBP foams in pulsating column technique after 25 successive pulses. Semiquantitative determination of bismuth (III) was also possible by this mode of extraction at constant number of pulses.
- iv. The selectivity of the proposed F2H2Dz-loaded foam on the detection of 1 µg of bismuth (III) in the presence of various interfering ions by batch mode of extraction was critically investigated.
Al-Mehrazi, Rashed Saleh, "Retention and Separation Behaviour of Chloropyrifos and Other Water Pollutants Using Polyurethane Foams" (1996). Theses. 394.