Recovery of Total Heavy Minerals from Badlands of Basanputti Village, Odisha

INTRODUCTION

Badlands form in areas of infrequent but intense rain-showers and sparse vegetation, a recipe for dev-astating erosion. In other way, badlands are a type of arid terrain with clay-rich soil that has been exten-sively eroded by wind and water. The landscape con-tains steep slopes, loose soil, and clay, all of which inhibit easy travel. Badlands usually have a spectacu-lar color display that alternates from dark black to red scoria/rusty red outflow of sediments. In arid conti-nental climates, these sediments are in direct contact with the atmosphere and oxidation is an important process, giving the sediment a red color. Red sediment contains very lean placer deposits for heavy mineral concentration, such as ilmenite, rutile, zircon, mona-zite, sillimanite, and garent. Red sediments are known in different terms, such as teri sands, erra dibbalu, and nalli hills, depending on the regions of east coast of India. Several authors studied on these deposits and concluded that the inland red sediment placer deposits exhibit a considerable variation in mineralogy and chemical composition depending on the location (Babu et al., 2009; Murty et al., 2007; Rao D S et al., 2005; Chandrasekharan and Murugan, 2001; Dwivedy, 1995; Krishnan et al., 1994; Rao and Rao, 1984).

The reddish/brown mountains visible just inland of India's eastern coast are part of the Eastern Ghats, which run from Tamil Nadu in the south through An-dhra Pradesh, Odisha, to West Bengal State in the north. Along the southeastern coast of India two very large deposits of 'teri' (red) sand and soil occur near Sattankulam and Kudiramojhi of southern districts of Tamilnadu, India. They are 2 to 10 km long, 100 m wide, and 10 m high. These deposits occur in semiarid and uninhabited rain shadow region of the western Ghat Mountains, 8 to 10 km interior from the shore-line. The average heavy mineral grade of these depos-its is approximately 10% with total heavy mineral (THM) reserves of 96 MT and an ilmenite reserve of 77 MT grade of ilmenite 6% in raw soil. Heavy, min-erals are concentrated in the -250+75 µm size fraction. Mineral assemblages of these resources contain, on average, 60%–70% ilmenite, 4%–6% rutile, 4% zircon, 16% sillimanite, and other minerals. Tata steel is pro-posed a Titania project over these deposits.

Along the Andhra Pradesh coast of India, four very large deposits of red sediment hillocks (erra deb-balu) occur near Visakhapatnam, Bheemunipatnam, Srikakulam, and Palasa covering approximately 200 km area, with the volume of the red sediment deposit ~145 million cubic meters. These red sediments are characterized by THM concentration of 10% to 25% (average), with ilmenite and sillimanite together ac-counting more than 90% of THM (Rao K N et al., 2008; Rao R B et al., 2006a; Rao N V N D et al., 1982). Trimax Industries commissioned a benefici-ation plant at Vastsavalasa, Srikakulam District, for the production of individual heavy mineral concen-trates from beach sands and red sediments.

The red sediments (nalli) hills of badland topog-raphy are extended throughout Puri, Khurda, Ganjam, and Chatrapur districts of Odisha. These deposits oc-cur in semiarid and habited regions away 10 to 20 km from the shoreline with heavy mineral concentration average ranging from 40% to 50% (THM), out of which 30% to 40% are ilmenite. The other heavy minerals sillimanite (3%–5%), zircon (1%–3%), rutile, garnet, monazite, and other minerals (< 2%) are in the order of abundance identified (Laxmi and Rao, 2010; Rao R B et al., 2010, 2006b; Routray and Rao, 2010; Rao Y et al., 1997; Gardner, 1981; Rao and Sriharia, 1980).

Scan of literature reveals that plenty of informa-tion available on the formation and mineral assem-blage of red sediments, but literature pertaining on recovery of total or individual heavy minerals is very much limited (Laxmi and Rao, 2010; Rao R B et al., 2010, 2006a, b; Routray and Rao, 2010; Babu et al., 2009; Rao K N et al., 2008; Murty et al., 2007; Rao D S et al., 2005; Chandrasekharan and Murugan, 2001; Rao Y et al., 1997; Dwivedy, 1995; Krishnan et al., 1994; Rao and Rao, 1984; Rao N V N D et al., 1982; Gardner, 1981; Rao and Sriharia, 1980). Any attempt to make use of these red sediments for the interest of the nation is an achievement from the point of view in industrialization, employment, and environmental is-sues. The red sediments of Basanputti Village, Ganjam District, Odisha, India, contain, on average, 71.8% THM, out of which 62.1% is ilmenite. Thus far, no attempt has been made to recovery heavy minerals on these deposits. Thus, an attempt to recover these THM and recovery of ilmenite is a future technology for the nation. In this article, an attempt is made to suggest a flowsheet to recover total valuable heavy minerals from these red sediments. A suggestion is also made to recover ilmenite mineral concentrate from the THM to use in pigment industries.

MATERIALS AND METHODS

Raw Material and Preparation

Red sediment samples were collected from bad-land topography of Basanputti, Ganjam District, Od-isha, which is shown in Fig. 1. Figure 1a shows typical red sediments' mound in the geographical re-gion of Ganjam District, Odisha. Figure 1b shows typical dendritic structure in the red sediments and concentration of heavies along the downstream flow of water. These sediment samples were collected in a grid pattern up to the water table level during rainy season. All the samples were thoroughly mixed and prepared a composite sample. Two subsamples were prepared by coning and quartering methods for (ⅰ) size analysis and (ⅱ) for scrubbing and desliming of large sample. Size analyses of as-received feed sample and scrubbed sample were carried out using standard sieves. Initially, the representative red sediment sam-ple was scrubbed and deslimed by using Hydrocyc-lone. The deslimed product sample was again subdi-vided into two samples for (ⅰ) characterization and (ⅱ) for beneficiation studies to recover THM.

Figure  1.  Topographical view of Basanputti red sediments.

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Methods

The deslimed sample was subjected to rougher, cleaner, and scavenging mineral separator circuits for recovery of THM. In the present investigation, Mozley laboratory mineral separator C800 'V' profile tray was used. The 'V' profile tray with 'end knock' could be able to accurately predict sand table per-formance when treating hydraulically classified prod-ucts. This would be of great value in the optimization of plant performance. An ~1 000 g sample was oper-ated on separator in batches. In each batch, 200 g sample was fed on the 'V' profile and wetted during the operation of the unit. The cyclic motion mobilizes the mineral particles enabling stratification to take place. The heavy (usually valuable) mineral settles and was 'thrown' upstream by the 'end-knock' action. The lighter (usually gangue) mineral was carried downstream by the flow of irrigation water to dis-charge via the tailings launder. It was observed partial separation of minerals after 0.5 min and complete separation after 3 min. The operating conditions such as deck angle and oscillation speed of the unit opera-tion and feed water and wash water were kept constant. Concentrates obtained were subjected to cleaner cir-cuits and tailings obtained were subjected to scaveng-ing circuits. The end product, THM recovered from the mineral separators, was dried and subjected to Perm roll dry low-intensity magnetic separator (DLIMS; at 0.6T magnetic intensity), as ilmenite is strongly magnetic, which could be easily separated out from other minerals by using DLIMS.

These size analysis products and all other sam-ples obtained from Mozley mineral separator (V-Tray) and Perm roll magnetic separator were subjected to sink-float tests to assess the total quality of the prod-ucts. Initially, sink-float tests were carried out with bromoform (CHBr₃; specific gravity 2.89) as a me-dium for separation of the heavier fractions from the lighter fractions. Methylene iodide (diidomethane; specific gravity 3.3) heavy medium was used to de-termine very heavy minerals (VHM) and light heavy minerals (LHM) from the THM. The percentage of total magnetic minerals present in the deslimed sam-ple was estimated by using Perm roll DLIMS (at 0.6T magnetic intensity).

Mineralogical modal analysis was carried out using a Leica petrological optical microscope. Pow-dered scrubbed product was subjected to X-ray dif-fraction (XRD) using PANalytical (X'pert) powder diffractometer (scan speed 1.2°/min from 6° to 40° by Mo Kα radiation) to identify the mineral phases.

RESULTS AND DISCUSSIONS

The mineralogical modal analysis of the sample shown in Fig. 2 indicates that the sample mainly con-tains ilmenite (62.1%) followed by sillimanite (7.2%), zircon (0.7%), garnet (0.6%), rutile (0.5%), and other heavy and gangue minerals (28.9%). The XRD data shown in Fig. 3 also confirm the findings that the sample contain ilmenite maximum followed by other minerals such as sillimanite, zircon, and rutile.

Figure  2.  Mineralogical modal analysis of Basan-putti red sediments.

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Figure  3.  XRD pattern of deslimed feed sample.

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Physical and chemical analysis of red sediments is given in Tables 1 and 2. The data given in Table 1 indicate that the sample contains 71.8% THM, out of which VHM (specific gravity > 3.3) are 64.0% and LHM (specific gravity > 2.86, < 3.3) such as sillimanite and other pyriboles are 7.8% by weight. The slimes present in the sample are 15.3% with 9.7% Fe (total iron). The total magnetic heavy minerals present in the sample are 62.7% and the total nonmagnetic heavy minerals are 9.1% by weight.

Table  1.  Physical properties of red sediment feed sample

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Table  2.  Chemical analysis of deslimed red sediment feed sample

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The chemical analysis of the deslimed feed sam-ple (Table 2) indicates that the sample contains 27.7% TiO₂, 99.9% Fe₂O₃, 14.2% Al₂O₃, and 0.9% ZrO₂. The data indicate that the sample contains appreciable amount ilmenite/rutile followed by sillimanite and zircon minerals.

Size analysis of feed and deslimed feed is shown in Fig. 4. The data indicate that deslimed feed is coarser (d₈₀=282 µm) than the feed (d₈₀=262 µm). It is as expected that because slimes contain 15%, which are washed out from the feed, the deslimed feed will be coarser.

Figure  4.  Size analysis of as-received feed and deslimed feed.

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The size analyses of THM in which VHM and LHM are present in the deslimed feed are shown in Fig. 5. The data indicate that both VHM and LHM follow the same size analysis pattern (d₈₀=240 µm). The size analysis of total magnetic and nonmagnetic heavy minerals in deslimed feed is shown in Fig. 6. The data indicate that total magnetic heavy minerals (d₈₀=240 µm) are almost close to the particle size range found for nonmagnetic heavy minerals (d₈₀=238 µm).

Figure  5.  Size analysis of THM, VHM, and LHM in deslimed feed. THM. Total heavy minerals; VHM. very heavy minerals; LHM. light heavy minerals.

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Figure  6.  Size analysis of total magnetic and non-magnetic heavy minerals in deslimed feed.

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Results of sequential sink-float studies on close sized fraction are given in Table 3. The data indicate that the THM are distributed maximum in -300+100 µm size fractions. This can clearly be seen in Fig. 7 where the distribution pattern of VHM and LHM is present in the deslimed feed.

Table  3.  Results of sequential sink-float studies on close sized fractions to recover THM, VHM and LHM

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Figure  7.  Distribution pattern of VHM and LHM in deslimed feed.

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Data given in Table 4 indicate the results of DLIMS (at 0.6T magnetic intensity) on close sized fraction. The findings indicate that total magnetic heavy minerals (62.7%) are distributed in the size fraction of -300+75 µm, whereas the nonmagnetic minerals present in -300+75 µm vary from 55.7% to 41.4% on average. This can clearly be seen in Fig. 8 where the distribution pattern of magnetic heavy min-erals and nonmagnetic heavy minerals is present in the deslimed feed.

Table  4.  Results of Dry low intensity magnetic separator on close sized fractions to recover magnetics and non-magnetics

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Figure  8.  Distribution pattern of magnetic and nonmagnetic heavy minerals present in deslimed feed.

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To recover THM, laboratory model mineral separator has been used. The rate of disappearance of tailings at every 30 s has been noticed. The rejectable tailings (4.1%–4.6% THM) could be achieved at 60 s. The results are given in Table 5 and the conceptual flowsheet with material balance is shown in Fig. 9. The total tailings contain 24.2% by weight, with 4.1% THM can be rejected. The product obtained contains 72.2% by weight with 94.4% THM and 95.0% recovery. The middling 3.6% by weight with 72.2% THM can be recycled for further recovery of THM. The ilmenite concentrate (Table 6) recovered by using DLIMS from the THM concentrate can be used in pigment industries after suitable pyrometallurgical/ chemical processing methods.

Table  5.  Summary of mineral separator studies on recovery of total heavy minerals

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Figure  9.  Flowsheet and material balance on recovery of THM from red sediments.

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Table  6.  Complete chemical analysis of the magnetic heavies (ilmenite mineral concentrate)

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CONCLUSIONS

The experimental studies carried out on red sediments of bad land topography of Basanputti Vil-lage, Ganjam District, Odisha, reveal that the red sediments contain 71.8% THM, out of which the VHM (specific gravity > 3.3) are 64% by weight, the LHM (specific gravity < 3.3) are 7.8% by weight, the total magnetic minerals are 62.7% by weight, and the total nonmagnetic minerals are 9.1% by weight. The sample also contains reddish colored slime (15.3% by weight and 9.7% total iron) and can be deslimed separately for value addition.

A flowsheet is suggested with material balance on the recovery of THM from rougher, scavenger, and cleaner mineral separator circuits. The results indicate that a combined product containing 94.4% THM with 72.2% yield and 95% recovery could be achieved. The ilmenite concentrate recovered by using DLIMS from the THM concentrate can be used in pigment indus-tries after suitable pyrometallurgical/chemical proc-essing methods.

ACKNOWLEDGMENTS

The authors are thankful to the Director, CSIR-Institute of Minerals and Materials Technology, Bhubaneswar, for giving permission to carry out this research work. One of the authors, Ms. T. Laxmi is thankful to CSIR for granting Senior Research Fel-lowship.