الفهرس 
Chapter IOnly 14 pages are availabe for public view
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Abstract
Due to its wide range of industrial applications and also its dangerous
environmental impact, boron attracted a large attention. The present work is
concerned with finding out a new resource for this important element in Egypt
where there is a very limited resource. Boron was discovered in different
industrial wastes e.g. borosilicate glasses, pyrexes and steel manufacturing.
However, boron is added in the manufacturing of these materials to do very
different important roles, where it is used to: reduce melting temperature (thus
to lower the energy consumed), increase fluidity (as a fluxing agent), increase
strength (harden ability) of the steel and reduce the corrosion of the refractory
material in the furnace. Almost of the added boron is getting out to the waste
and is able to recycle. Thus the author tries to recycle this important element
from the slag waste of steel manufacturing. For this purpose a sample weight
of 50Kg of the waste slag was collected from Helwan steel factory.
The geochemical investigations of the representative sample by using
both of XRF and SEM analysis techniques shows the presence of major
elements such as: Fe, Ca, Mg, Si. While the complete chemical analysis
revealed that it assays 10.8% of SiO2, 2.2% of MgO, 28.7% of Fe2O3, 7.6%
MnO, 0.8% of B2O3 and 45.9% of CaO as well as it shows considerable
concentration of valuable elements such as: 500ppm of Mo and 300ppm of V.
At high temperatures in the high tower of the steel factory B and Si would
form refractory borosilicate compounds. The dissolution of B from such
refractory compounds would be achieved by applying the alkali fusion
procedures followed by washing the fused matrix with diluted alkaline
solution to dissolve its B content.
For optimizing the fusion parameters several fusion reagents such as:
Na2CO3, NaOH, KOH, NaHCO3 and a mixture of (Na2CO3+ NaHCO3) wasinvestigated. The mixing weight ratio between the sample and the reagent
(S/R) weight ratio was also studied. As well as both the fusion time and
fusion temperature of the fused matrix was also investigated. Results of this
study show that the alkali fusion with Na2CO3 was effective at the following
optimum fusion conditions: S/R weight ratio of 1/1.5, a fusion temperature of
900 ºC and a fusion time period of 30 min. Application of these conditions
upon a 200g weight of the working B waste slag sample yielded an alkaline
leach liquor assaying 0.4 g/l of B and 3 g/l of Si with achieved dissolution
efficiencies of 80% and 30%, respectively. The latter was directed to the
extraction columns which packed with the B selective resin Purolite S108 for
recovering its B content.
By adjusting the pH value of the prepared alkaline solution to a value
of pH 7 using drops of conc. H2SO4, Si ions in the latter was directly
precipitated with an achieved precipitation efficiency of 99% in the form of
SiO2-gel. This precipitate was washed with 25ml of distilled H2O during
filtration to avoid the loss of 20% from the dissolved B by adsorption on its
outer surface. The washing solution was then added to the filtrate of the
alkaline B feed solution. The precipitate of SiO2-gel should be removed
because it might coat the exchange sites of the B ion selective resin. The
precipitate of SiO2-gel was ignited at 850ºC for 1h and left to cool and then
washed. After dryness a 6.4g weight of SiO2 was recovered with achieved
recovery efficiency up to 99%. The produced SiO2 was identified using XRD
analysis technique.
The alkaline solution free from Si was then used to extract B however
the maximum loading efficiency of 91.2% was achieved at pH 9 and working
flow rate of 1ml/min. The loaded B at these conditions achieved a percentage
of 95.1% of the theoretical capacity of the present resin (3g B/L wsr resin).
The loaded B was eluated achieved elution efficiency of 91.2% by sing 3%H2SO4 solution and applying a flow rate of 1ml/min which are the elution
optimum conditions.
The final product boric acid was already prepared from the obtained B
concentrated eluate solution by crystallization through gentle thermal
evaporation. The application of the B extraction process on the remained B
alkaline feed solution leads to extract more than 95% of the presented B(OH)-
4 as pure boric acid. The produced boric acid was identified by using X-ray
diffraction analysis technique.
The leaching.