Heated blends of phosphate waste: Microstructure characterization, effects of processing factors and use as a phosphorus source for alfalfa growth.
Microstructure of expandable lightweight aggregates (LWAs), which was composed of phosphate waste (PW), cement kiln dust (CKD) and raw clay (RC) was investigated, and the effects of processing factors (temperature, waste content, soaking time) on their physical properties were quantified by using response surface methodology (RSM). The potential use of LWAs as a phosphorus source was assessed through the use of seeds of alfalfa. It was found that the main minerals of the waste, namely carbonates and fluorapatite, were involved in the formation of labradorite/anorthite and melt respectively. Stability of mullite- the main constituent of CKD- was sensitive to the melt content. The assemblage of the identified phases was discussed based on the CaO-SiO2-Al2O3 phase diagram. The results of RSM showed that the change of compressive strength, firing shrinkage and water absorption of LWAs versus processing factors was well described with a polynomial model and the weights of the effects of the factors increased in the following order: sintering temperature > waste content (in the case of PW-RC) > soaking time. On the other hand, it was found that due to the release of phosphorus by soil-embedded pellets, the growth of alfalfa plants improved, and the rate enhanced in this order: PW-RC > PW-CKD > PW-CKD-RC. The absorbed quantity of phosphorus (0.12%) was still lower than the common uptake amount.
LPCME, URAC20, Université Cadi Ayyad, Faculté des Sciences Semlalia, Bd. Prince My Abdellah, B.P. 2390, 40001 Marrakech, Morocco; LCME, Université Cadi Ayyad, Faculté des Sciences et Techniques, Av. A. Khattabi, B.P. 549, 40000 Marrakech, Morocco; IM2NP, Institut des Matériaux Microélectronique Nanosciences de Provence, Université du Sud Toulon-Var, Bât. R e B.P. 20132, 83 957 La Garde Cedex, France.
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Loutou
LPCME, URAC20, Université Cadi Ayyad, Faculté des Sciences Semlalia, Bd. Prince My Abdellah, B.P. 2390, 40001 Marrakech, Morocco. Electronic address: hajjaji@uca.ma.
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Hajjaji
LCME, Université Cadi Ayyad, Faculté des Sciences et Techniques, Av. A. Khattabi, B.P. 549, 40000 Marrakech, Morocco.
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Mansori
IM2NP, Institut des Matériaux Microélectronique Nanosciences de Provence, Université du Sud Toulon-Var, Bât. R e B.P. 20132, 83 957 La Garde Cedex, France.
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Favotto
LCME, Université Cadi Ayyad, Faculté des Sciences et Techniques, Av. A. Khattabi, B.P. 549, 40000 Marrakech, Morocco.
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Hakkou
D000538:Aluminum Silicates / Q000737:chemistry; D000077215:Clay; D004391:Dust; D000455:Medicago sativa / Q000254:growth & development* / Q000378:metabolism; D010710:Phosphates / Q000737:chemistry*; D010758:Phosphorus / Q000378:metabolism*; D012639:Seeds / Q000254:growth & development; D012822:Silicon Dioxide / Q000737:chemistry; D012987:Soil / Q000737:chemistry; D013696:Temperature; D014866:Waste Products; D014867:Water / Q000737:chemistry
D000538:Aluminum Silicates; D004391:Dust; D010710:Phosphates; D012987:Soil; D014866:Waste Products; D014867:Water; C074225:anorthite; C049037:aluminosilicate; D010758:Phosphorus; D012822:Silicon Dioxide; D000077215:Clay
Alfalfa growth; LWAs; Microstructure; Phosphate waste; Physical properties; Response surface methodology