DESC:The present disclosure generally relates to a method for processing red mud.
BACKGROUND
Red mud is a toxic waste product produced during refining of bauxite to yield alumina. Alumina produced is used as a raw material for obtaining aluminum by the Hall–Héroult process. As the percentage of alumina found in bauxite ore is generally between 30-50%, approximately one to two tons of red mud is generated for every one ton of alumina produced. Being toxic and produced in large quantities, red mud poses a huge challenge for disposal.
Conventionally, red mud produced is pumped into clay-lined dams or dykes, and allowed to dry naturally. The operation of these conventional disposal areas is simple and inexpensive, but has significant impact on the environment. Moreover, such conventional method requires large open land for disposal of red mud that causes additional problems especially for refineries with limited land space.
There have been several attempts made to neutralize red mud and return it to soil as a harmless material. Chinese patent application No. CN101816280 for example describes a process wherein red mud and molasses alcohol waste liquid are mixed together and fermented in presence of anaerobes in a cement tank for obtaining soil suitable for disposal. This process is however not suitable for large scale deployment as it requires additional equipment.
Therefore, there is a need for a method for processing red mud to obtain processed red mud that may be disposed without causing any environmental hazard. Moreover, such method should be easy to carry out and be industrially viable.

SUMMARY
A method of processing red mud is disclosed. The method comprises of mixing red mud with acidic soil to obtain a mixture of red mud and acidic soil, mixing the mixture of red mud and acidic soil with spent wash, and drying the mixture so obtained to obtain processed red mud having pH in a range of 6 to 8.5.

DESCRIPTION
For the purpose of promoting an understanding of the principles of the invention, reference will now be made to embodiments and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the disclosed process, and such further applications of the principles of the invention therein being contemplated as would normally occur to one skilled in the art to which the invention relates.
It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not intended to be restrictive thereof.
Reference throughout this specification to “one embodiment” “an embodiment” or similar language means that a particular feature, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrase “in one embodiment”, “in an embodiment” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.
The present disclosure generally relates to a method for processing red mud.
As used herein, “red mud”, or bauxite residue, is a waste by-product produced when bauxite is refined to produce alumina. The red mud generally has a pH in the range of 11.8 to 10.5.
The method for processing red mud comprises mixing red mud with acidic soil and raw spent wash from sugar distillery to obtain processed red mud.
“Acidic soil” as used herein refers to soil having a pH in the range of 5.9 to 6.5.
“Raw spent wash from sugar distillery” as used herein means raw liquid effluent produced from sugar industries and/or distilleries producing ethyl alcohol from various raw materials especially molasses derived from cane sugar. Such spent wash contains carbonic acid in addition to other by-products and has a pH in a range of 3.5 to 4.2. The “Raw spent wash from sugar distillery” herein after is referred to as “Spent Wash”.
The processed red mud obtained from this process has a neutral or near neutral pH. Specifically, the processed red mud obtained from the process has a pH in a range of 6 to 8.5. Such processed red mud having a pH in a range of 6 to 8.5 can be disposed without causing any environmental hazard. The processed red mud may also be mixed with soil to increase soil fertility.
The method for processing red mud comprises of mixing red mud with acidic soil to obtain a mixture of red mud and acidic soil. Dry red mud may be mixed with dry acidic soil to obtain the mixture of red mud and acidic soil. Alternatively, for homogeneous mixing red mud and acidic soil are mixed using water. The red mud and the acidic soil may also be crushed in case of lumps prior to mixing. The mixture of red mud and acidic soil is then dried. In accordance with aspect, the mixture of red mud and acidic soil may be allowed to stand/rest for a predetermined period of time. For example for 3 to 6 days. The mixture of red mud and acidic soil obtained has a pH of approximately 9.9. The red mud and acidic soil are mixed in a ratio from 1: 4.5 to 1:9 weight/weight.
The method further comprises of mixing the mixture of red mud and acidic soil with spent wash to obtain a wet mixture of red mud, acidic soil and spent wash.
In accordance with an aspect, the mixture of red mud and acidic soil may be mixed with the spent wash such that the ratio of red mud : acidic soil : spent wash is in a range of 1:1:1 to 1:4:5 weight/weight.
The wet mixture thus obtained is dried to obtain processed red mud. The wet mixture may be dried till the moisture content of the processed red mud is reduced to an acceptable level and till the pH of the processed red mud reaches near neutral before it is returned to the environment. The mixture of red mud and acidic soil may be mixed with the spent wash in a ratio that would allow the pH of the processed red mud obtained to be in a range of 6 to 8.5.
In accordance with an embodiment, the red mud may be washed with water prior to mixing with acidic soil to obtain washed red mud. Such washed red mud may then be mixed with acidic soil and spent wash to obtain the processed red mud.
The following example(s) of the method of processing red mud are exemplary and should not be understood to be in any way limiting.

Example 1:
Table 1: Details of ingredients:
Sl. No. Ingredient Description pH Remark
1 Red Mud sample 11.69 Dry red mud sample from red mud pond
2 Soil sample-1 6.69 Collected from a portion of land near village Kucheipadar not under cultivation.
3 Soil sample-2 6.01 Collected from a portion of land near village Kucheipadar under cultivation.
4 Spent Wash 4.0 Effluent from Sugar Factory (Raw Spent wash)

Experiment No. A
1. Dry Red Mud was washed with tap water of same volume and dried in open atmosphere.
2. After washing the red mud, the water (spent water has a pH of 11.5) is mixed in equal proportion with Industrial effluent ( Spent Wash).
Result:
1. pH of washed/leached Red Mud = 10.8
2. pH of water used to wash red mud = 11.5
3. pH of mixture of Spent water (water used to leach red mud) and Spent Wash (1:1) = 6.3
Experiment No. B
Leached red mud (pH =10.8) is mixed with soil sample-1 in the ratio of 1: 4.5vol/vol [i.e. one part (165grams) red mud and 4.5 parts (697.5grams) soil sample -1 having pH 6.69)]. For homogeneous mixing red mud and soil sample are crushed and mixed using equal volume (104 milliliters) of tap water. The mixture is dried in open atmosphere for 4 days.
The resultant pH of mixture obtained in Experiment B having red mud and acidic soil in a ratio of 1: 4.5 is 10.
Experiment No. C
Leached red mud (pH =10.8) is mixed with soil sample-1 in the proportion of 1: 9 [i.e. one part (165grams) red mud and 9 parts (1395grams) soil sample -1]. For homogeneous mixing red mud and soil sample is crushed and mixed using equal volume (104 milliliters) of tap water. The mixture is dried in open atmosphere for 4 days.
The resultant pH of mixture obtained in Experiment C having red mud and acidic soil in a ratio of 1: 9 is 9.9.
Experiment No. D
Leached red mud (having pH =10.8) is mixed with soil sample-2 in the proportion of 1: 4.5 [i.e. one part red mud (165grams) and 4.5 parts (697.5grams) soil sample -2 having pH =6.01]. For homogeneous mixing red mud and soil sample is crushed and mixed using equal volume (104 milliliters) of tap water. The mixture is dried in open atmosphere for 6 days.
The resultant pH of mixture obtained in Experiment D having red mud and acidic soil (Soil Sample-2) in a ratio of 1: 4.5 is 9.64.
Experiment No. E
Leached red mud (having pH =10.8) is mixed with soil sample-1 in the proportion of 1: 9 [i.e. one part (165grams) red mud and 9 parts (1395grams) soil sample -1]. For homogeneous mixing red mud and soil sample is crushed and mixed using equal volume (104 milliliters) of tap water. The mixture is dried in open atmosphere for 6 days.
The resultant pH of mixture obtained in Experiment E having red mud and acidic soil (Soil Sample-1) in a ratio of 1: 9 is 9.285.
Experiment No. F
Leached red mud (having pH =10.8) is mixed with spent wash (pH=4.0) in the proportion of 1: 1 (on volumetric basis) [i.e. one part (165grams) leached red mud and one part (125grams) spent wash]. The mixture is dried in open atmosphere for 6 days.
The resultant pH of the mixture obtained in Experiment F is 9.64.
Experiment No. G
Red mud (having a pH =11.69) is mixed with spent wash (pH=4.0) in the proportion of 1: 1 (on volumetric basis) [i.e. one part (165grams) red mud and one part (125grams) spent wash]. The mixture is dried in open atmosphere for 4 days (similar to experiment run, F).
Resultant pH of the mixture obtained in Experiment G is 9.8.
Experiment No. H
Leached red mud (having pH =10.8) is mixed with spent wash (pH=4.0) in the proportion of 1: 1 (on volumetric basis) [i.e. one part (165grams) leached red mud and one part (125grams) spent wash]. The mixture is dried in open atmosphere for 9 days (Similar to run F and G).
Resultant pH of the mixture obtained in Experiment H is 9.4.
Experiment No. I
The mixture obtained from Experiment C is mixed with spent wash of same quantity (volumetric basis) and dried in the open atmosphere for 3 days. The ratio of leached red mud: soil sample-1: spent wash is 1:9:10 [i.e. one part (165grams) red mud, nine parts (1395 grams) of soil sample-1 and ten parts (1250 grams) spent wash].
The resultant pH of processed red mud obtained in Experiment I is 5.73.
Experiment No. J
The mixture obtained from Experiment E is mixed with spent wash of same quantity (volumetric basis) and dried in the open atmosphere for 3 days. The ratio of leached red mud: soil sample-1: spent wash is 1:9:10 [i.e. one part (165grams) red mud, nine parts (1395 grams) of soil sample-1 and 10 parts (1250 grams) spent wash].
The resultant pH of processed red mud obtained in Experiment J is 6.38.
Experiment No. K
Leached red mud (pH =10.8) is mixed with soil sample-1 in the proportion of 1: 9 (i.e. one part red mud (165 gram) and nine parts (1395grams) soil sample -1). For homogeneous mixing red mud and soil sample are crushed and mixed using equal volume (104 milliliters) of tap water. The mixture is dried in open atmosphere for 4 days.
The mixture of red mud and soil sample-1 obtained is mixed with spent wash of same quantity (volumetric basis) and dried in the open atmosphere for 3 days. The ratio of leached red mud: soil sample-1: spent wash is 1:9:10 [i.e. one part (165grams) red mud, nine parts (1395 grams) of soil sample-1 and ten parts (1250 grams) spent wash].
The resultant pH of processed red mud obtained in Experiment K is 5.73.
Experiment No. L
Leached red mud (having pH =10.8) is mixed with soil sample-1 in the proportion of 1: 9 [i.e. one part (165 gram) red mud and 9 parts (1395grams) soil sample -1]. For homogeneous mixing red mud and soil sample crushed and mixed using equal volume (104 milliliters) of tap water. The mixture is dried in open atmosphere for 6 days.
The mixture obtained is mixed with spent wash of same quantity (on volumetric basis) and dried in the open atmosphere for 3 days. The ratio of leached red mud: soil sample-1: spent wash is 1:9:10 [i.e. one part (165grams) red mud, nine part (1395grams) of soil sample-1 and ten parts (1250 grams) spent wash].
The resultant pH of processed red mud obtained in Experiment L is 6.38.

Example 2:
Reactants/ Ingredients:
Table 2: Constituents of Reactants
Table 2A
Sample ID Acidic Soil (AS) Red Mud (RM)
Source Collected from a farm in village Kucheipadar, Odisha Collected from a Red Mud Pond of the plant of Utkal Alumina International Limited, Doraguda, Rayagada, Odisha
% TA 16.77 12.81
% SiO2 47.36 4.10
% Fe2O3 15.42 63.84
% TiO2 0.43 4.35
% CaO 0.11 1.52
% Na2O 0.71 2.28
% P2O5 0.217 0.18
% V2O5 0.025 0.13
pH 5.95 11.05

Table 2B
Raw Distillery Spent Wash collected from a distillery in, Kopargaon, Maharashtra.
Sample ID COD Mg/L pH
DSW 86843 4.20

Constituents of the reactants were tested in laboratory of Utkal Alumina International Limited, Doraguda, Rayagada, Odisha. pH measured by Systronics 362 (3 Point Calibration) make Systronics India, Ahmedabad. Chemical Analysis done on PANalytical, Netherland make XRF (X-Ray Fluorescence Spectrometer). The analysis was done on the basis of % by Mass Only.

The following experiments were conducted:
Experiment 1: 400 grams of raw distillery spent wash (DSW) was mixed with 400 grams of Acidic Soil (AS), i.e., in a 1:1 proportion on mass basis. The resultant pH was measured on 59th day. The resultant pH was 7.2
Experiment 2: 400grams of raw distillery spent wash (DSW) was mixed with 400 grams of Red Mud (RM) i.e., in a 1:1 proportion on mass basis. The resultant pH was measured on 47th day. The resultant pH was 9.
Experiment 3: 400 grams of raw distillery spent wash (DSW) was mixed with 400 grams of Red Mud (RM ) and 400gms of acidic soil, i.e., in a 1:1:1 proportion on mass basis. The resultant pH was measured on 47th day. The resultant pH was 6.8.
Experiment 4: 1000 grams of raw distillery spent wash (DSW) was mixed with 200 grams of Red Mud and 800 grams of acidic soil (AS) in 5:1:4 proportion on mass basis. The resultant pH was measured on 47th day. The resultant pH was 7.

Table 3: Results of the experiments conducted:
Sample
ID Reactants Ratio (wt/wt) Exact Weight (gm) No of days the mixture was allowed to stand Resultant pH
1. DSW:RM 1:1 400 each 59 days 9.0
3. DSW:AS 1:1 400 each 47 days 7.2
4. DSW:RM:AS 1:1:1 400 each 47 days 6.8
5. DSW:RM:AS 5:1:4 1000:200:800 47 days 7.0

The results of the experiments conducted indicate that treating red mud with raw distillery spent wash and acidic soil results in processed red mud having near neutral pH.

Example 3:
Reactants:
1. DSW1 - Raw distillery spent wash collected from a distillery, in Kopargaon Maharashtra
2. DSW2 - Raw distillery spent wash collected from a distillery, in Shrikakulam, Andhra Pradesh
3. RM - Red Mud collected from a Red Mud Pond of the plant of Utkal Alumina International Limited, Doraguda, Rayagada, Odisha
4. AS – Acidic Soil collected from a farm in village Kucheipadar, Odisha
5. TW – Tap water

Table 4: Constituents of Reactants
Table 4A
Sample ID Acidic Soil (AS) Red Mud (RM)
Source Collected from a farm in village Kucheipadar,Odisha Collected from a Red Mud Pond of the plant of Utkal Alumina International Limited, Doraguda, Rayagada, Odisha
% TA 16.77 12.81
% SiO2 47.36 4.10
% Fe2O3 15.42 63.84
% TiO2 0.43 4.35
% CaO 0.11 1.52
% Na2O 0.71 2.28
% P2O5 0.217 0.18
% V2O5 0.025 0.13
pH 5.95 11.05
*Testing done at Lucid Laboratory, Hyderabad

Table 4B
DSW1 (Raw distillery spent wash collected from a distillery in Kopargaon, Maharashtra)
Proximate Analysis (%by mass) Ultimate Analysis (%by mass)
PH (10% aq. solution) Moisture Ash Volatile matter Fixed carbon Moisture Ash Carbon as C Hydrogen as H Nitrogen as N Sulphur as S Oxygen as O
4.28 93.93 1.21 3.32 1.54 93.93 1.21 1.58 2.4 0.07 0.16 0.65

Table 4C
DSW2 Raw distillery spent wash collected from a distillery in Srikakulam, Andhra Pradesh
Proximate Analysis (%by mass) Ultimate Analysis (%by mass)
PH (10% aq. solution) Moisture Ash Volatile matter Fixed carbon Moisture Ash Carbon as C Hydrogen as H Nitrogen as N Sulphur as S Oxygen as O
4.08 92.86 1.5 4.17 1.47 92.86 1.5 1.5 2.75 0.14 0.18 1.07
Test Method: IS: 1350, Instrument Used: PH Meter.

The following experiments were conducted:

Experiment 1. 4 kilograms of DSW1, 4 kilograms of acidic soil and 4 kilograms of red mud were mixed [ 1:1:1 proportion on mass basis]
Experiment 2. 4 kilograms of DSW2, 4 kilograms of acidic soil and 4 kilograms of red mud were mixed [ 1:1:1 proportion on mass basis]
Experiment 3. 4 liters of tap water, 4 kilograms of acidic soil and 4 kilograms of red mud were mixed

Table 5: Results of the experiments conducted
Experiment ID Mixture Proportion
(by weight) pH
Experiment 1 (DSW1:RM:ACIDIC SOIL) 1:1:1 8.81
Experiment 2 (DSW2:RM: ACIDIC SOIL) 1:1:1 8.45
Experiment 3 (TW:RM: ACIDIC SOIL) 1:1:1 10.38
Chemical Analysis – PANalytical, Netherland make XRF (X-Ray Fluorescence Spectrometer).
Analysis is done on the basis of % by Mass Only.

The results of the experiments conducted indicate that treating red mud with raw distillery spent wash and acidic soil results in processed red mud having near neutral pH irrespective of the source of raw distillery spent wash.

Example 4:
Reactants:
1. DSW1 - Raw distillery spent wash collected from a distillery in Kopargaon, Maharashtra
2. DSW2 - Raw distillery spent wash collected from a distillery, in Shrikakulam, Andhra Pradesh
3. RM - Red Mud collected from a Red Mud Pond of the plant of Utkal Alumina International Limited, Doraguda, Rayagada, Odisha
4. AS – Acidic Soil collected from a farm in village Kucheipadar, Odisha
5. TW – Tap water

The following experiments were conducted:
Various experiments were conducted by mixing together ingredients in the quantities as mentioned in the table below. The pH of the resultant mixture was measured and is indicated in the table below as resultant pH.

Table 6: Results of the experiments conducted
Experiment no. (Sample
ID) Ingredients Ratio Exact Weight Resultant pH
1 DSW1:RM 1:1 400 gm each 9.0
2 DSW1: AS 1:1 400 gm each 7.2
3 DSW1:RM:AS 1:1:1 400 gm each 6.8
4 DSW1:RM:AS 5:1:4 1000gm:200gm:800gm 7.0
5

DSW1:RM
(Same sample tested over a period of time to observe changes in pH) 1:2 650 gm:1300 gm

1st day 8.94
10th day 9.32
45th day 9.82
1 DSW2:RM 1:1 400 gm each 9.1
2 DSW2: AS 1:1 400 gm each 7.4
3 DSW2:RM:AS 1:1:1 400 gm each 7.2
4 DSW2:RM:AS 5:1:4 1000gm:200gm:800gm 6.7
5 DSW2:RM:AS 5:1:4 1000gm:200gm:800gm 6.47

Specific Embodiments:
A method of processing red mud comprising mixing red mud with acidic soil to obtain a mixture of red mud and acidic soil; mixing the mixture of red mud and acidic soil with spent wash; and drying the mixture so obtained to obtain processed red mud having pH in a range of 6 to 8.5.
Such method(s), wherein the ratio of red mud: acidic soil: spent wash is in a range of to 1:1:1 to 1:4:5 on weight basis.
Such method(s), wherein the mixture of red mud and acidic soil is obtained by a process comprising mixing red mud and acidic soil; adding water to the red mud and acidic soil followed by mixing; and drying the mixture to obtain the mixture of red mud and acidic soil.
Such method(s), wherein the red mud and acidic soil are crushed prior to addition of water.
Such method(s), wherein the ratio of water: crushed red mud and acidic soil is in a range of 1:1:1 on weight basis.
Such method(s), wherein the mixture of red mud and acidic soil are allowed to stand for a period of 3 to 6 days prior to mixing with spent wash.
Such method(s), wherein the method further comprises washing red mud with water prior to mixing with acidic soil.

INDUSTRIAL APPLICABILITY
The method for processing red mud as disclosed allows for processing red mud in an easy and industrially viable method. The processed red mud obtained from this process has a pH that is near neutral or neutral. This allows the processed red mud to be disposed without causing any environmental hazard. Moreover, the processed red mud when mixed with the soil may enhance the fertility of soil. Additionally, the processed red mud obtained with this method has improve cohesiveness among the red mud crystals due to the addition of spent wash. Due to the improved cohesiveness the processed red mud is suitable for construction purpose. Further as the method uses spent wash which is also an industrial effluent, the disposal of spent wash is also addressed with the disclosed process.
,CLAIMS:We claim:

1. A method of processing red mud comprising:
mixing red mud with acidic soil to obtain a mixture of red mud and acidic soil;
mixing the mixture of red mud and acidic soil with spent wash; and
drying the mixture so obtained to obtain processed red mud having pH in a range of 6 to 8.5.

2. A method as claimed in claim 1, wherein the ratio of red mud: acidic soil: spent wash is in a range of 1:1:1 to 1:4:5 on weight basis.

3. A method as claimed in claim 1, wherein the mixture of red mud and acidic soil is obtained by a process comprising:
mixing red mud and acidic soil;
adding water to the red mud and acidic soil followed by mixing; and
drying the mixture to obtain the mixture of red mud and acidic soil.

4. A method as claimed in claim 3, wherein the red mud and acidic soil are crushed prior to addition of water.

5. A method as claimed in claim 3, wherein the ratio of water: crushed red mud and acidic soil is in a range of 1:1:1 on weight basis.

6. A method as claimed in claim 3 wherein the mixture of red mud and acidic soil are allowed to stand for a period of 3 to 6 days prior to mixing with spent wash.

7. A method as claimed in claim 1 or 3, wherein the method further comprises washing red mud with water prior to mixing with acidic soil.

Dated this 8th day of August, 2014

Aparna Kareer
Of Obhan & Associates
Agent for the Applicant
Patent Agent No. 1359