Beneficiation of White Kaolinitic Sandstone to Produce Kaolin Concentrate from Wadi Siq-Rakyia Area in Wadi Araba, Jordan

Kaolinitic sandstone samples of Lower Cretaceous from Wadi Siq-Rakyia area in Wadi Araba/south of Jordan were studied and assessed as a source of Kaolin. Three channel samples and a composite bulk sample were studied for their mineralogical, geochemical, and grain size distribution analysis. The aim of this research work was to achieve kaolin concentration by examining the best-suited and cost-effective processing method(s) with appropriate product recovery. Following the initial sample characterisation at “bench scale”, a pilot study was performed on the bulk sandstone sample. Kaolin was accumulated in the fine size fraction (−125 µm) after agitating and wet screening of the sample. The −125 µm size fraction sample was used to produce kaolin concentrate. Hydrocyclone classification was applied in the pilot study for this purpose. The mass flowrate of the feeds and the products in the hydrocyclones was calculated for the bulk sample as well as the amount of water required operating the process. A kaolin-enriched product was produced following the use of hydrocyclones. A kaolin concentrate at a grade of 71% and a recovery of 78% was produced which could be used in the ceramic industry for tableware and sanitaryware.

kaolin in the sandstone samples and to assess its possible industrial applications.
The research study was intended to characterize, evaluate, and to beneficiate the raw material of the kaolinitic sandstone. The study consists of characterization of the raw materials which define the mineralogical, physical and chemical properties, upgrading of the mineral to achieve quality and recovery, and then applying pilot study in order to design and model effective processing method. Lithology of the kaolinitic sandstone outcrops are very fine, fine to medium-grained, angular, sub-angular to sub-rounded grains, friable, soft and partly reworked massive white sandstone containing scattered quartz pebbles and granules with white clay matrix. This lithology may result from crushing and subsequent weathering in a strongly deformed zone. The depositional environment of the lower part is interpreted as braided to meandering river channels (indicated by the presence of the channel-fill sandstone) with brief marine intrusions over the alluvial plain [1].

Geology, Location and Description of Samples
Three kaolinitic sandstone samples were taken from trenches excavated in the outcrops representing a thickness of 15 -20 m. The sandstone samples are actually friable, poorly cemented sandstone with kaolinite clay mineral as matrix.
Kaolinitic clays (thin seams) are interbedded within the sandstone beds (Table   1). A composite bulk sample for pilot study was collected from the same location. All samples were bagged, transported to Aqaba port, and shipped to the laboratory of the School at the University of Nottingham in UK.

Preparation
The studied samples are friable sand with small sandstone lumps, which are easily breakable with little energy. There was no need for any crushing to reduce the A detailed laboratory work was conducted to study the grain size analysis, the mineralogical variation and contents, the chemical components of the raw samples, and the dry and the wet sieved fractions (Figure 1). The results of this stage will be used as a foundation for the next evaluation and processing steps. Kaolinitic sandstone (KS3) sample was chosen to carry out the detailed characterisation study due to the fact that this sample represents the whole sequence of the deposit as well as the bulk sample.

Particle Size Analysis
Different methods of size analysis were employed in different stages of the study.
Sieving technique was extensively used in this stage. In addition, other techniques, such as sedimentation and laser-sizer were also used in other stages.
Dry and wet sieve analyses were performed on the kaolinitic sandstone sample. The particle size distribution was determined using a set of sieves of aperture sizes of 1180, 850, 600, 425, 300, 212, 150, 106, 75, 53, and 38 μm. The weight retained on each sieve of dry and wet sieving was measured and the weight percentage was calculated [2]. The results of the weight percentage retained on each sieve are listed in Table 2.
The results of the kaolinitic sandstone sample are presented in cumulative and frequency distribution curves. For the purpose of plotting, the points on the cumulative and frequency curves are plotted in between two successive sieve sizes.
The cumulative undersize of the dry and the wet sieving of (KS3) sample shows that the median size (d 50 ) of the sample is about 190 μm, which indicates that the kaolinitic sandstone sample is mainly fine-grained size. The results indicate that the sand is poorly sorted ( Figure 2).
The frequency distribution curves of the dry and the wet sieving of the KS3 sample show that the weight retained on sieve 212 μm has slightly increased from about (16.8%) in the dry sieving to about (18.6%) in the wet sieving. This increase could be explained due to the washing of the clay material from the surface of the grains that has dislodged the lumps and liberated the particles ( Figure 3).   It is noticed from Table 2 of the KS3sample that the weight retained on the 38 μm sieve was decreased from 6.4% in the dry sieving to 3.1% in the wet sieving.
This indicates that water has washed down the fine materials and the clay size particles to the −38 µm fraction.
The fine particles in the −38 μm wet sieve fraction constitute about 9.1% in weight of the whole rock. The fine material was analysed to determine the particle size distribution using "Mastersizer S" laser technique. The results have shown that 65% is less than 15 µm and 33% is less than 5 µm of this fraction, which stands for 6% and 3% of the whole sample respectively ( Figure 4).

X-Ray Diffraction (XRD) Examination
The whole rock and the −38 µm dry sievedsize fraction of the (KS3) sample were      (Figure 7).

Scanning Electron Microscopy (SEM)
The Scanning Electron Microscope (SEM) technique was used to visualise the shape, size and morphology of the particle's surface. It was also used to identify the mineral components of the clay size fraction.
The kaolinite mineral plates were found in stacks on the surface or cementing the quartz grains. The SEM photograph of the kaolinite plates shows coarse to very fine euhedral to subhedral plates and well crystalline shape ( Figure 8).

Geochemical Study
The chemical analysis for the major standard elements was carried out using X-Ray Fluorescence (XRF) spectrometry and the fusion bead moulding technique was employed for preparation test samples. The results of the chemical analysis of the whole rock samples are displayed in Table 3, while the wet and the dry sieved fractions of the (KS3) sample are listed in Table 4.

Preparation
The results of mineralogical, chemical and grain size analysis of the −38 and −2 µm size fractions of the kaolinitic sandstone (KS3) confirmed that kaolinite was the only clay mineral found in the sample. The cumulative undersize curve showed that the fine fraction (−125 µm) contained about 34% by weight of the KS3 sample and the percentage of kaolinite increased towards the finer size fractions. Therefore, it was necessary to study this fraction in detail with a view to recovering kaolin.
The wet screened −125 µm fraction of the bulk sample was subjected to classification trials using hydrocyclone classifiers. The use of hydrocyclones was to produce fine size fraction in order to concentrate kaolin as a product. A sedimentation method was also applied to concentrate kaolin in the −5 µm size fraction. Figure 9 illustrates the procedures of kaolin concentration from the −125 µm fraction.

Hydrocyclone Classification
Hydrocyclone is a continuously operating classifying device, which utilises centrifugal force to accelerate the settling rate of the particles [3].
Two types of Mozley hydrocyclones were used. A 2-inch (50.8 mm) diameter hydrocyclone was employed to produce an overflow of "expected" −15 µm size fraction and another 10 mm diameter one used to produce an overflow of approximately −5 µm in size.   Table 5).
The results showed that the mass flowrate of dry solids in the 2-inch hydrocyclone was 205.2 kg/hr for the feed and 63 kg/hr for the overflow. The yield or recovery of solids to the overflow was 30.7% and in the underflow was 69.3%, while the weight of water recovered was about 78% and 22% for the overflow and underflow respectively.
The overflow product from the 2-inch unit was used as feed for the 10 mm hydrocyclone. The feed was adjusted to a solid concentration of 4% -5% by weight and fed at a pressure of 100 psi using a 2 mm vortex finder and 1 mm spigot. It was stated that using the smallest vortex finder, highest inlet pressure and low feed pulp density produce the finest cut point (d 50 ) [4].
A 20-second sample was collected from the overflow and underflow streams.
The wet and dried samples were weighed and the percentage solids by weight, yield and the mass flowrate in kg/h were calculated (Table 6).

Sedimentation Fractionation
In another attempt to try to concentrate the kaolin in finer fraction, the overflow from the 2-inch hydrocyclone was used to produce a concentrate of −5 µm in size using the conventional sedimentation technique [5].
The results of the chemical analysis showed that the Al 2 O 3 content of the −5 and 5 -15 µm size fractions was 29.48% and 28.22% respectively ( Table 7). The very close values would reflect poor refining as the quantity of kaolin in these fractions would be in direct proportion to the Al 2 O 3 content. The results revealed that concentrating kaolin by refining method would not produce a high kaolin concentration in the fine fraction. This was probably due to the wide range of the particle size distribution present in the sample (from less than 1 µm

Analytical Results of the Products
The wet screened −125 µm size fraction and the overflow products from the 2-inch and 10 mm hydrocyclones were examined to determine the chemical, mineralogical and particle size analysis using XRF, XRD and Laser sizing techniques.
The  Table 9 are in good agreement with those in Table 8.   The results of the trace element analysis showed low values. Slightly high values of strontium (Sr) and sulphur (S) were noticed in the overflow products, which probably indicated the presence of Celestine (SrSO 4 ) heavy mineral as a source of strontium (Table 10).
The mineralogical investigation using XRD showed that quartz and kaolinite were the only minerals found in the wet screened fraction and the hydrocyclone products. The mineralogy of the overflow of the 10 mm hydrocyclone showed that although kaolinite was the major constituent, quartz still existed as a minor ( Figure 11). It is indicated that very fine quartz particles (less than 5 µm) were recovered with kaolin in the overflow product.

Kaolin Grade and Recovery
As quartz was the only impurity provided that any heavy minerals present did  Figure 11. XRD trace of the overflow from the 10 mm hydrocyclone (K-kaolinite, Q-quartz). Open Journal of Geology 100% kaolin content would contain 39.49% by weight of Al 2 O 3 and therefore, the kaolin quantity in the products was calculated in proportional to the Al 2 O 3 content as a ratio of (100:39.49).
Based on the results of the 20-second time samples from the 2-inch and 10 mm hydrocyclones (see Table 5 & Table 6), the kaolin grade and recovery results were calculated and are tabulated in Table 11. It was found that the 2-inch hydrocyclone recovered to the overflow 78% kaolin at a grade of 71% from the −125 µm fraction. The 2-inch overflow was fed to the 10 mm hydrocyclone and recovered 32% at a grade of 82.5% to the overflow stream.
It should be mentioned that there was still a considerable amount (68% recovery at a grade of 69%) of kaolin in the underflow product of the 10 mm hydrocyclone. Returning this underflow to the feed would probably increase the recovery of kaolin to the overflow. However, this was not part of the current work.
Based on the results of Table 11, the dry weight and recovery of the overflow products for the 2-inch and 10 mm hydrocyclones were calculated based on the dry weight of the wet screened −125 µm fraction. The results are displayed in Table 12. The results showed that the kaolin grade (content) increased from 21% by weight in the −125 µm size fraction to 82% by weight in the 10 mm hydrocyclone overflow product while the recovery decreased from 43% to 14% ( Figure   12).

Hydrocyclone Efficiency
The partition curve is the commonest method of representing hydrocyclone efficiency and is constructed by plotting the percentage of each particle size by weight in the feed, which reports to the underflow, against the particle size. Ref.
[4] defined the cut point or d 50 size (separation size) as the point on the partition curve for which 50% of the particles in the feed of that size report to the underflow. Partition curves can be used to predict the products that would be obtained if the feed or separation size were changed. In all classifiers, it is assumed that solids of all sizes are entrained in the coarse product (underflow) liquid by short-circuiting in direct proportion to the fraction of feed water reporting to the underflow. Therefore, the partition curve can be corrected by utilising the following equation [8]: y' is the corrected mass fraction of a particular size reporting to underflow, y is the actual mass fraction of that size, R is the fraction of the feed liquid (water) recovered in the underflow.
The fraction (R) of the feed liquid recovered in the underflow was calculated in the separation processes of the two hydrocyclones (see Table 5 & Table 6).
The fraction was 21.6% and 24.4% in the separation process of kaolin by the 2-inch hydrocyclone and the 10 mm hydrocyclone respectively. This meant that of the feed material in the 10 mm hydrocyclone. Therefore, the percentage of feed recovered to the underflow should be corrected in proportion to that short-circuiting fraction.
In the 2-inch hydrocyclone, the mass balance calculation of the products showed that the percentage of the feed (yield) which reported to the overflow was 31% and 69% to the underflow. The weight percentages of the particle size analysis of the products (i.e. overflow and underflow), the partition coefficient (% of feed to U/F), and the corrected partition coefficient are tabulated in Table   13. The results of the uncorrected and corrected of the percentage of feed to the underflow are plotted against the nominal size and illustrated in Figure 13. The results showed that the cut point (d 50 ) was 12 µm while the corrected cut point d 50(C) increased to 16 μm.
In the 10 mm hydrocyclone, the mass balance calculation of the products showed that the percentage of the feed (yield) which reported to the overflow and the underflow was 28.2% and 71.8% respectively. The weight percentage of the particle size analysis of the products (i.e. overflow and underflow), the partition coefficient (% of feed to U/F), and the corrected partition coefficient are presented in Table 14.
The results of the corrected and uncorrected of the percentage of feed to the underflow are plotted against the nominal size and illustrated in Figure 14. The results showed that the cut point (d 50 ) was 2.2 µm and the corrected d 50(C) was 3.9 µm.

Assessment of the Kaolin Product
The overflow and the underflow products from the 2-inch and 10 mm hydrocyclones were tested by WBB Company [6] for number of physical properties.
The results of the size distribution and quantity of minerals are presented in Table 15, while the brightness and colour measurements are shown in Table 16.
Brightness is defined as the ratio, expressed as percentage, of the radiation reflected by a body to the radiation reflected by a perfect reflecting standard (e.g. The fired brightness of 90.2 for the 10 mm hydrocyclone overflow was probably partly due to a low degree of vitrification because of the low alkali (Na and K) content of the product. The good results of the fired brightness were encouraging for its potential use in the ceramic industry whereas the raw brightness was less important.
The silica alumina ratio was a little higher than desirable as the alumina content should ideally be more than 35% -36%. The iron oxides content was considered low when compared with typical products. The results of the kaolin product are displayed against commercial kaolin products used as fillers and in the ceramic industry (Table 17).   Kaolin for paper manufacturing has to meet stringent specifications with regard to brightness, viscosity, particle size distribution, and abrasiveness. Due to the relatively high amount of quartz and low raw brightness, it is not expected that the concentrated kaolin would meet the paper manufacturing specification.
As filler, further classifying would be necessary to reduce the amount of fine quartz and increase the kaolinite content in order to upgrade it to the required specification. In the ceramic industry, despite the good fired brightness, low iron oxides, and accepted grain size distribution, the kaolinite content was still marginal for porcelain production. However, it could be used for other types of ceramic such as tableware, sanitaryware and earthenware when the results were compared with other kaolin produced by WBB.

Discussion and Conclusions
The −125 µm size fraction of the kaolinitic sandstone (KS) sample was used to produce a kaolin concentrate product. Hydrocyclone classification was used in the pilot study for this purpose.
A kaolin concentrate at a grade of 70.6% and a recovery of 77.7% was produced from the −125 µm fraction of the kaolinitic sandstone. The overflow kaolin product was classified by the 2-inch (50.8 mm) diameter hydrocyclone at a dry mass flowrate of 0.063 tph. In the 10 mm diameter hydrocyclone, the overflow kaolin concentrate at a grade of 82.5% and a recovery of 32% was classified from the overflow of the 2-inch (50.8 mm) hydrocyclone. The product was produced at dry mass flowrate of 0.002 tph.
A continuous operation of 2-inch and 10 mm hydrocyclones working in a plant at 16 hours a day, 300 days a year, would produce a kaolin product as follows: The mass balance calculation for the 2-inch hydrocyclone (see Table 5) showed that the feed dry mass flowrate was 0.21 tph producing an overflow (d 50 of 16 µm) of 0.06 tph (300 tpa) at a grade of 70.6% and a recovery of 77.7%. For the 10 mm hydrocyclone, the mass balance calculation (see Table 6) showed that the feed dry mass flowrate was 0.007 tph producing an overflow (d 50 of 3.9 µm) of 0.002 tph (9.5 tpa) at a grade of 82.5% and recovery of 32%.
These results showed that for each ton of the kaolinitic sandstone, an amount of 0.1 t of a kaolin-enriched fraction at a grade of 70.6% or an amount of 0.003t of a kaolin-enriched fraction at a grade of 82.5% could be produced.
Due to the relatively excess amount of fine quartz grains and low raw material brightness (71.5), the kaolin product was not expected to be used in the paper industry. The high fired ISO brightness (90.2) of the kaolin concentrate was due to a low degree of vitrification because of the low alkali (Na and K) content in the product. The good results of the fired brightness were encouraging for the material to be used in the ceramic industry. Open Journal of Geology

Conflicts of Interest
The author declares no conflicts of interest regarding the publication of this paper.