Soil Science Society of America Journal 67:837-843 (2003)
© 2003 Soil Science Society of America
DIVISION S-5—PEDOLOGY
Improvement of the Successive Selective Dissolution Procedure for the Separation of Birnessite, Lithiophorite, and Goethite in Soil Manganese Nodules
Y. Tokashiki*,a,
T. Hentonab,
M. Shimob and
L. P. Vidhana Arachchib
a Professor of Soil Science and Land Conservation, Dep. of Environmental Science and Technology, Faculty of Agriculture, Univ. of the Ryukyus, Nishihara- cho, Okinawa 903-0213, Japan
b Senior Soil Scientist, Coconut Research Institute, Lunuwila, Sri Lanka
* Corresponding author (toka2841{at}agr.u-ryukyu.ac.jp)
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ABSTRACT
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A successive selective dissolution procedure was improved to distinguish two Mn oxide minerals namely, birnessite (Bs) and lithiophorite (Lp) from Fe oxide minerals in soil Mn nodules. Soil Mn nodules collected from Typic Hapludalfs in Okinawa Island, Japan, were dissolved using successive NaOH, hydroxylamine hydrochloride (HAHC), and dithionite-citrate-bicarbonate (DCB) reagents at various temperatures. A test sample was prepared by mixing synthetic Bs, Lp (USNM#8811), natural gibbsite (Gb) and goethite (Ge), and soil clay containing kaolinite, illite, and vermiculite-chlorite intergrade mineral and used as a comparative standard. The NaOH treatment was able to dissolve kaolinite and Gb, concentrated the Bs, Lp, and Ge in the comparative sample. The HAHC treatment at 25°C effectively dissolved Bs but Lp and Ge remained undissolved. A subsequent extraction with HAHC at 60°C dissolved Lp without disturbing Ge. Finally, the DCB treatment was able to dissolve Ge. Thus, extraction with HAHC at 25 and 60°C were useful in distinguishing Bs and Lp respectively from Fe oxides minerals. The proposed method can also be applied to distinguish Mn, Fe, and Al oxide minerals in Fe-Mn nodules of natural soil.
Abbreviations: Bs, birnessite • DCB, diothionite-citrate-bicarbonate • Gb, gibbsite • Ge, geothite • HAHC, hydroxylamine hydrochloride • Lp, lithiophorite ore • XRD, x-ray diffraction
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INTRODUCTION
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MANGANESE NODULES IN SOILS, although in small quantity, are potential sources of Mn, Fe, Co, Ni, Cu, and other minor elements for plant nutrient up take. Manganese minerals in soils can be also effective scavengers of trace elements. The chemical properties of Mn minerals have been studied in detail (Taylor et al., 1964, Michalyna, 1971; Burns, 1976; Norman et al., 1996). Chemical properties, occurrence, and formation of Mn minerals have also been thoroughly reviewed by Taylor (1987) and Mc Kenzie (1989).
Distinguishing different Mn minerals in soils by x-ray diffraction (XRD) is difficult because of their poor crystallinity. X-ray diffractometry to distinguish Mn minerals in soils and Fe-Mn concretions can be limited because of the masking and coincidence of peaks of Mn minerals with those of quartz, illite/mica, and kaolinite (Gallaher et al., 1973). McKenzie (1989) reported that because of the small quantities of Mn minerals present in soils, XRD method can only be used when natural segregation of the minerals occur, such as in nodules or veins. Tokashiki et al. (1986) used a combination of successive selective dissolution and XRD methods to separate Bs from Lp of the clay fraction of Mn nodules by using concentrated NaOH to dissolve kaolin minerals. Then, HAHC treatment at 25°C was successfully used to dissolve Bs. However, separation of Lp from Ge was not successful. Goethite strongly binds with Mn minerals and is widespread in different climatic regions (Boero et al., 1992). Therefore, the present study was aimed to (i) separate Lp from Ge, and (ii) distinguish Bs and Lp in nodules developed from natural soils by improving the successive selective dissolution method.
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MATERIALS AND METHODS
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Sample Used as a Test Material and Soil Manganese Nodules
The Mn nodules used in this study were collected from soils derived from limestone in Okinawa, Japan (Table 1). Clay fraction (<2 µm) of the MN-1 and MN-4 nodule samples was used as the reference (Table 1) in the development of the successive selective dissolution procedure of the study. Composition of this sample was determined by the previous successive selective dissolution procedure developed by Tokashiki et al. (1986), and it contained Bs, Lp, Ge, kaolinite, illite, vermiculite-chlorite intergrade mineral, and Gb.
A mixture of Bs, Lp, Ge, and soil clay minerals containing kaolinite, illite,vermiculite-chlorite intergrade mineral, and Gb was prepared as a test sample by mixing soil clay, MN-4, Na-Bs, and Lp (Table 2). The artificial mixture had a weight ratio of 44:2:2:2 for soil clay/MN-4/Na-Bs/Lp. The contents of this mixture were gently ground using an agate mortar and pestle.
The mineralogy of the samples MN-1 and MN-4 used in Tokashiki et al. (1986) was similar to those of MN-14, MN-15, and MN-16 used in this study. Our procedure was then applied to separate the Lp from Ge in natural Mn-nodule samples of MN-14, MN-15, and MN-16 (Table 1) to verify its effectiveness.
Improvement of the Successive Selective Dissolution Procedure
The successive selective dissolution procedure developed in this study consists following: (i) 50 mg of the <2-µm Mn-nodule sample was placed in each of five 10-mL Teflon centrifuge tubes; (ii) four out of five tubes were treated with 10 mL of 5 M NaOH, mixed using ultrasonifier for 10 s, and placed in a water bath for 60 min at 90 to 95°C to dissolve kaolinite and Gb minerals. The remaining tube was separated as the control. Samples treated with NaOH were allowed to cool to room temperature and then centrifuged for 10 min at 1500 x g. Decanted the supernatants and residues were then washed with 8 mL of distilled water using ultrasonifier for 10 s to remove excess base, when treating the residual material with 0.1 M HAHC (25°C). One of these residues was then separated as the NaOH treated sample; (iii) 10 mL of 0.1 M NH2OH.HCl (HAHC) was then added to the remaining three tubes and ultrasonified for 10 s, and then shaken at 25°C for 10 min to dissolve Bs. The treated samples were again then centrifuged for 10 min at 1500 x g and one was separated as the 0.1 M HAHC (25°C) treated sample; (iv) The residues in the remaining two tubes were treated with 0.1 M HAHC at 60°C for 30 min. This condition was developed for the sample MN-1 with the 0.1 M HAHC treatment testing a series of temperature namely, 25, 40, 50, 60, and 70°C (Fig. 1)
. Then these two tubes were allowed to cool to room temperature and were centrifuged and decanted and one tube was separated as the 0.1 M HAHC (60°C) treated sample; (v) The last sample was treated with DCB and ultrasonified for 10 s and placed in a water bath for 15 min at 80°C to dissolve Ge before centrifugation as proposed by Mehra and Jackson (1960) and considered as the DCB-treated sample. Supernatant in each step except NaOH-treated supernatant of samples MN-14, MN-15, and MN-16 was used for elemental analysis.
X-Ray Diffraction Analysis
Each sample following extraction was suspended in H2O and dried on a glass slide, then analyzed by XRD from 2 to 30° 2
using CuK
radiation at 30 kV and 10 mA. Phyllosilicates were also determined by XRD on DCB pretreated samples in absence of NaOH treatment. The XRD analysis was done on oriented clays after Mg2+– and K+–saturation. Magnesium-2+ saturated clay was then x-rayed in air-dried conditions and after glycerol solvation. The K+–saturated air-dried clay samples were x-rayed after progressive heating at 105, 300, and 550°C.
Determination of the Dissolved Elements
The supernatants collected by centrifuge samples after each treatment of the successive selective dissolution (except NaOH-treated supernatant) were adjusted to 50 mL by adding distilled water, and stored in refrigerator in a 100-mL polyethylene bottle before wet digestion. A 10-mL aliquot of the extract was placed into a 100-mL kjeldahl flask and 15 mL of concentrated HNO3 and 10 mL of concentrated HClO4 was added. It was then placed on a kjeldahl digester until the completion of digestion as observed by the dark color of solution being gradually converted to transparent light green color with evolution of white fumes. Elemental analysis was conducted using atomic absorption spectrophotometer (AAS).
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RESULTS AND DISCUSSION
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Dissolution of Lithiophorite
The XRD patterns of the MN-1 sample (Table 1) containing mainly Lp, Ge, and illite obtained by the successive selective dissolution treated with 0.1 M HAHC at various temperatures are indicated in Fig. 1. The untreated sample showed peaks at 0.945 (Lp), 0.472 (Lp), 0.417 (Ge), and 0.334 nm. The 0.5-M NaOH treatment produced a significant increase in Lp peaks at 0.945 and 0.472 nm. The NaOH treatment was able to concentrate Mn oxides in Mn nodule without recrystallization. Hydroxylamine hydrochloride treatment at 25°C had no effect, both peaks appeared at 0.945 and 0.472 nm. We increased the temperature in the water bath through a series of steps (40, 50, 60, and 70°C) to determine the appropriate temperature for dissolution of Lp. No affect was observed after 40°C. We observed a decrease in both the 0.945- and 0.472-nm peaks after treatment at 50°C, and both were completely collapsed after treatment at 60 and 70°C. These treatments did not affect the Ge peak at 0.417 nm. The HAHC treatment at temperature higher than 60°C did not affect Ge as shown in the XRD pattern. According to the results, it is suggested that the treatment of HAHC at 60°C for 30 min was able to dissolve Lp.
Separation of Lithiophorite from Goethite in the Artificial Mixed Sample
Figure 2
shows the XRD patterns of the artificial sample are separate and composite mineral fractions in the artificially mixed sample. Soil clay sample contained illite (peaks of 1.00, 0.501, and 0.335 nm), kaolinite (0.725), and Ge (0.417 nm). Mn nodule (MN-4) contained Bs (0.724 and 0.358 nm), Lp (0.947 and 0.472 nm), Gb (0.485 nm), Ge (0.417 nm), kaolinite (0.725 nm), and illite, which were not clear in the XRD pattern. Synthetic Na-Bs gave peaks at 0.72 and 0.358 nm. Lithiophorite ore have peaks at 0.947 and 0.472 nm. The position of the peaks of Lp (0.947 and 0.472 nm) and Bs appeared in artificial sample are similar to that of artificial mixed sample of the soil clay (Fig. 2).
The dissolution of the Mn minerals in the artificially mixed sample was accompanied by a corresponding disappearance of the XRD peaks. Hence Fig. 3
can be used to evaluate the effectiveness of the developed successive selective dissolution procedure to separate Mn minerals from Ge. The NaOH treatment usually used to dissolve kaolinite and Gb, resulted in an increase in intensity and sharpness of some of peaks. This result is similar to that of the NaOH treatment of MN-1 (Fig. 1). Figure 3 shows that treating of the NaOH residue with HAHC at 25°C for 10 min resulted in the disappearance of Bs peaks at 0.724 and 0.358 nm. The HAHC at 60°C for 30 min only resulted in a decreased intensity of XRD peaks of Lp (0.946 and 0.472 nm), but it did not cause their complete disappearance in artificial mixed sample. After repeating of HAHC (60°C) treatment, the peaks of Lp were collapsed indicating the Lp was dissolved completely. The repetition of the HAHC treatment at 60°C for 30 min to complete the dissolution of the Lp suggested that minerals in the artificial sample have a high degree of crystallinity. It might be that the mineral was from an ore. The similar phenomenon with this data was shown in the XRD pattern of Lp ore (Tokashiki et al., 1986). Further treating the HAHC residue at 60°C for 30 min with DCB resulted in a collapsed of the peak of Ge, which appeared at 0.418 nm. But the peaks of the clay minerals illite at 1.00, 0.501, and 0.335 nm respectively were retained. Results generated from this study (Fig. 3) suggested that the use of HAHC treatment at 60°C for 30 min period in a water bath could be used to separate Lp from Ge.
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Fig. 3. X-ray diffraction of artificial mixed sample treated by the proposed selective dissolution procedure.
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Application of the New Procedure to Natural Soil Manganese Nodule
To test the validity of the improved method, the procedure was applied to separate Lp from Ge in the natural soil Mn nodules of MN-14, MN-15, and MN-16 (Table 1). The XRD patterns of the untreated sample comprised a series of peaks at 0.947, 0.472, 0.418, and 0.334 nm. The peaks at 0.947 and 0.472 could be probably due to Lp, while, the peaks at 0.418 and 0.334 nm represented the minerals of Ge and layer silicate minerals respectively (Fig. 4X)
. The NaOH treatment resulted in a clear peak of each mineral in XRD pattern. The HAHC followed by 0.5 M NaOH treatment at 25°C resulted in the dissolution of Bs (0.725 nm) while the peaks of Lp (0.947 and 0.472 nm) and Ge (0.418 nm) were retained. Subsequently the peaks of Lp (0.947 and 0.472 nm) were collapsed by the treatments of the HAHC at 60°C for 30 min, leaving Ge. Ultimately, the peak of Ge was collapsed by the DCB treatment. Figure 4Y shows the XRD pattern of parallel oriented clays of the MN-14 sample after Mg2+– and K+–saturation. According to the pattern of XRD, it is suggested that the main phyllosilicates present in this nodule were illite, kaolin mineral, and vermiculite-chlorite intergrade mineral. Because of heating, the 1.4-nm peak showed a gradual reduction of intensity and shifted to 1.0 nm representing of vermiculite-chlorite intergrade mineral. Besides these phyllosilicates, Gb (0.485 nm) was also represent in the Mn-nodule. The results of the successive selective dissolution of the sample of MN-15 are similar to that of MN-14 (Fig. 5X and 5Y)
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Fig. 4. X-ray diffraction of MN-14 treated by successive selective dissolution (X) and with diothinite-citrate bicarbonate (DCB), without NaOH treatment (Y). 1, Untreated; 2, NaOH; 3, NaOH + HAHC (25°C); 4, NaOH + HAHC (60°C); 5, NaOH + HAHC (60°C) + DCB; A, Mg-clay air-dried; B: Mg-clay glycerol-saturated; C, K-clay air-dried; D, K-clay 105°C; E, K-clay 300°C; F, K-clay 550°C.
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Fig. 5. X-ray diffraction of MN-15 treated by successive selective dissolution (X) and with diothinite-citrate bicarbonate (DCB), without NaOH treatment (Y). 1, Untreated; 2, NaOH; 3, NaOH + HAHC (25°C); 4, NaOH + HAHC (60°C); 5, NaOH + HAHC (60°C) + DCB; A, Mg-clay air-dried; B: Mg-clay glycerol-saturated; C, K-clay air-dried; D, K-clay 105°C; E, K-clay 300°C; F, K-clay 550°C.
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Figure 6
shows the XRD pattern of the successive selective dissolution of the sample MN-16. The results are not as definitive as those represented in Fig. 4 and 5. The peaks with very low intensities in sample MN-16 appeared at 0.947 and 0.472 nm suggesting the presence of the Lp. However, both peaks were not enhanced with NaOH treatment because of their poor crystallinity (Ross et al., 1976; Mcdaniel and Boul, 1991). The concentration of illite and kaolin minerals are much more than vermiculite-chlorite intergrade mineral in samples of MN-14 and MN-15, however, concentration of illite and kaolin minerals are almost similar to vermiculite-chlorite intergrade mineral in sample of MN-16 (Table 3).
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Fig. 6. X-ray diffraction of MN-16 treated by successive selective dissolution (X) and with diothinite-citrate bicarbonate (DCB), without NaOH treatment (Y). 1, Untreated; 2, NaOH; 3, NaOH + HAHC (25°C); 4, NaOH + HAHC (60°C); 5, NaOH + HAHC (60°C) + DCB; A, Mg-clay air-dried; B: Mg-clay glycerol-saturated; C, K-clay air-dried; D, K-clay 105°C; E, K-clay 300°C; F, K-clay 550°C.
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Table 3. Mineralogical compositon of the soil Mn-Nodules resulted by the developed successive dissolution procedure.
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Semi-Quantitative Analysis of Manganese and Iron Oxide Minerals
Semi-quantitative analysis of the oxide-minerals composing the Mn nodule (MN-14, MN-15, and MN-16) was conducted by a combination of extractable Fe, Mn, and Al by each extraction for the purpose of changing XRD pattern. As Bs could be dissolved by the HAHC at 25°C, the content of this mineral was determined in the extract corresponding to the collapse of peak at 0.725 nm. Similarly, extractable Mn by HAHC determined Lp at 60°C in which the peak at 0.947 and 0.472 nm disappeared and the Fe content was likewise determined in the DCB extract to represent Ge. Gibbsite did not give a peak on the successive selective dissolution, but it was present as a peak at 0.485 nm in the parallel-oriented clay on the Mg2+– and K+–saturated clays. All the samples showed that the content of extractable Mn by HAHC (25°C) was 80 to 90% indicating the presence of Bs. The extractable Mn by HAHC (60°C) was 10 to 20% indicating the presence of Lp. The extractable Fe by the DCB treatment that was suggested as Ge was 80 to 90%. The extractable Al by each treatment including DCB extract should be depended on amorphous silicate minerals (Tokashiki and Wada, 1975; Wada, 1989). Table 4 also shows that the total Fe, Mn, and Al as a result of summation of each element extracted by the HAHC (25°C), HAHC (60°C), and DCB treatment. In addition, XRD analysis gave clear peaks of Bs and Lp for both samples of MN-14 and MN-15 because of their high crystalinity, while that of not clear in MN-16 sample because of their poor crystalinity (Fig. 6X). However elemental analysis of these three samples was not shown significant differences with respect to successive dissolution procedure (Table 4). Over all results explained that the proposed procedure is able to characterize the peak intensities of Mn minerals in XRD analysis and which was extremely useful to distinguish the Mn minerals from Ge in the natural soil Mn nodules.
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CONCLUSIONS
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Use of NaOH, as a pretreatment is necessary to concentrate Mn oxide minerals and dissolve kaolinite and Gb minerals, thereby increase the peak intensities of Bs and Lp. Lithiophorite was selectively dissolved by the HAHC solution at 60°C while Ge remained. Goethite was dissolved effectively by DCB leaving layer silicate of illite and vermiculite-chlorite intergrade mineral. The new supplementary procedure of successive selective dissolution provides methods to semi-quantify Bs and Lp in the presence of layer silicates and other oxide minerals.
Received for publication January 16, 2001.
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REFERENCES
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- Boero, V., A. Premoli, P. Melis, E. Barberis, and E. Arduino. 1992. Influence of climate on the iron-oxide mineralogy of Terra Rossa. Clay Clay Miner. 40:8–13.[Abstract]
- Burns, R.G. 1976. The uptake of cobalt into ferromanganese nodules, soils, and synthetic manganese (oxides). Geochim. Cosmochim. Acta 40:95–102.
- Gallaher, R.N., H.F. Perkins, K.H. Tan, and D. Radcliffe. 1973. Soil concretions: II. Mineralogical analysis. Soil Sci. Soc. Am. Proc. 37:469–472.
- McDaniel, P.A., and S.W. Boul. 1991. Manganese distribution in acid soils of the North Carolina Piedmont. Soil Sci. Soc. Am. J. 55:152–158.[Abstract/Free Full Text]
- McKenzie, R.M. 1989. Manganese oxides and hydroxides. p. 439–465. In J.B. Dixon and S.B. Weed (ed.) Minerals in soil environments. SSSA Book Series 1. SSSA, Madison, WI.
- Mehra, O.P., and M.L. Jackson. 1960. Iron oxide removal from soils and clays by dithionite-citrate system buffered with sodium bicarbonate. Clays Clay Miner. 7:317–327.
- Michalyna, W. 1971. Distribution of various forms of aluminum, iron and manganese in the orthic gray wooded, gleyed orthic gray wooded and related gleysolic soils in Manitoba. Can. J. Soil Sci. 51:23–36.
- Ross, S.J., D.P. Franzmeer, and C.B. Roth. 1976. Mineralogy and chemistry of manganese oxides in some Indiana soils. Soil Sci. Soc. Am. J. 40:137–143.
- Taylor, R.M. 1987. Non-silicate oxides and hydroxides. P. 173–189. In A.C.D. Newman (ed.). Chemistry of clays and clay minerals. Mineralogical Society, Longman Scientific & Technical, UK.
- Taylor, R.M., R.M. McKenzie, and K. Norrish 1964. The mineralogy and chemistry of manganese in some Australian soils. Aust. J. Soil Res. 2:235–248.
- Tokashiki, Y. 1976. Clay minerals in potter's earth for an Okinawa pottery, Tsuboya-yaki (In Japanese.) Sci. Bull. Coll. Agri. Univ. Ryukyus 23:153–164.
- Tokashiki, Y., J.B. Dixon, and D.C. Golden. 1986. Manganese oxide analysis in soils by combined X-ray diffraction and selective dissolution methods. Soil Sci. Soc. Am. J. 50:1079–1084.[Abstract/Free Full Text]
- Tokashiki, Y., and K. Wada. 1975. Weathering implications of the mineralogy of clay fractions of two Ando soils, Kyushu. Geoderma 14:47–62.
- Wada, K. 1989. Allophane and Imogolite. p. 1051–1087. In J.B. Dixon and S.B. Weed (ed.) Minerals in soil environments. SSSA Book Series 1. SSSA, Madison, WI.
- White, G.N., and Dixon, J. B. 1996. Iron Manganese distribution in nodules from a young Texas vertisol. Soil Sci. Soc. Am J. 60:1254–1262.[Abstract/Free Full Text]
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ABSTRACT
INTRODUCTION
