Production of Silicomanganese Alloy from Low Manganese Containing Leached Sea Nodules Residue

Leached sea nodules residue was used for the present study for exploring its utilization. The residue generated in ammoniacal-SO2 pressure leaching was water washed to reduce the sulphur content. To improve the Mn/Fe ratio in the residue, it was blended with Fe-Mn slag or Mn ore in the calculated amount and smelting was carried out in 50 kVA submerged arc furnace. Various parameters such as holding time, amount of reductant, power input etc. were investigated. The maximum recovery of Mn from residue blended with Fe-Mn slag and Mn ore was 58% and 65% respectively in the form of silicomanganese

Lead sorption by sea nodule residue generated in reduction roasting – ammonia leaching.

Residue generated in reduction roast – ammonia leaching of sea nodules has been utilised for the remediation of aqueous lead. Characterization of sea nodule residue (SNR) reveals fine granulometry (d50 = 11.4 µm) and high surface area of 66.7 m2 g-1. Batch adsorption experiments have been performed varying different parameters. Equilibrium experimental data fitted well in the Langmuir isotherm and derived maximum adsorption capacity (qm) of lead onto SNR has been found to be 840.34 mg Pb(II)/g SNR at 303 K. The qm enhanced to very high value of 2500 mgPb/gSNR upon raising the temperature to 323 K. The pseudo second-order model has been found applicable to the lead removal kinetics

Iron oxide waste to clean arsenic-contaminated water.

Serious manifestations of arsenic toxicity in majority of human population consuming contaminated water has led to development of number of remedial methods including adsorption onto iron oxide based natural and synthetic materials. Iron oxide adsorbents generated as waste in industrial processes may be utilised for arsenic remediation. These adsorbents can be considered better in terms of least production cost as well as minimal environmental implications. Here, we studied arsenic removal from contaminated water using iron oxide wastes generated in pickling unit of a steel plant. The iron oxide obtained by steel pickling was subjected to controlled reduction in fluidised bed reactor using gaseous reductant producing magnetic iron oxide. Prior to adsorption studies, physicochemical characterisation of both the iron oxides was undertaken. This was followed by batch equilibrium and kinetics adsorption tests to investigate arsenic (V) removal properties. Several parameters such as time, pH, arsenic concentration, adsorbent dose etc were investigated using synthetic solutions. Arsenic affected ground water samples collected from West Bengal (India) were also tested using both iron oxide adsorbents. Experimental results showed more than 90% arsenic removal within 10 min, not depending on pH of water with appreciable loading (0.12-0.17 mg As/g) on both adsorbents. Presence of anions such as SO42-and PO43- adversely affected arsenic adsorption. While testing real ground water samples, initial arsenic level of 0.010–0.018 mg/L was brought down to 0.002–0.008 mg/L. Our study has established potential use of an industrial waste for the removal of arsenic (V) from water

Different applications of waste generated in reduction roasting – ammonia leaching of manganese nodules.

CSIR-NML, Jamshedpur has been engaged in technology development to recover valuable metals (Cu, Ni & Co) from manganese nodules (MN). Extensive R&D work led to development of a process based on reduction roast – ammonia leaching – solvent extraction (SX) – electrowining (EW) route. This process generates large amount of waste/residue (70% of the MN weight) after selective leaching of Cu, Co and Ni, which may be considered hazardous, if untreated, due to its fineness and heavy metal contents. Characterisation studies have shown that this leaching residue waste contains oxides/oxyhydroxides of Fe, Mn, Al and Si with a high porosity and surface area, which are suitable for catalytic activity and adsorption of various aqueous pollutants. In addition, appreciable amount of manganese content of the manganese nodule leached waste may be recovered for the improvement of the economics of MN processing. Keeping these in view, studies for utilisation of waste leach residue have been carried out in three different ways: i) The use of leaching residue as catalyst has been successfully assessed for decolourisation of methylene blue (MB). The surface complex between wMNR and MB at a rate limiting step followed by electron transfer from MB to active metal centre of wMNR and release of products has been found to be operative during the decolourisation process. ii) The potential of water washed leaching residue as adsorbent has been evaluated for removal of anionic pollutants phosphate (PO43-), selenite (SeO32-) and cationic pollutants like Cu2+ and Cd2+, showing a maximum phosphate uptake of 9.88 mgP g-1 and selenite uptake of 15.17 mg Se g-1 for wMNR calcined at 400 C. The monolayer adsorption capacities (Qo) has been found to be temperature dependent showing 26.95 mg g-1 and 40.32 mg g-1 at 303 and 323 K, respectively for Cu2+ ion while the values are 32.23 and 38.14 mg g-1 at 303 and 323 K, respectively for Cd2+ adsorption. iii) In the third application of leached residue, a value added material like silicomanganese alloy has been produced by smelting of MN leaching waste in a 50 kVA electric arc furnace, with manganese recovery of about 77%

Thermodynamics and Viscosity aspects in Manganese Nodule Residue Smelting for Silicomanganese Production

Among several under trial processes for extraction of base metals (Cu, Co and Ni) from manganese nodules (M79, the reduction-roast ammoniacal leaching {N1140H/ (NH4)2CO3) process is considered very attractive. After the leaching of base metals from roast-reduced MN, a substantial quan-tity of residue left behind (about 70 wt. % by mass) as wastes for disposal or further use. Smelting studies showed that leached manganese nodules residue (WMNR) can be successfully utilized as raw material for silicomangan-ese production after maintaining proper metallurgical aspects like thermodynamics, viscosity etc Literature survey on slag liquidus and viscosity aspects of silicoman-ganese smelting has been done. The slag liquidus has been found to be closely associated to slag basicity i.e. (Ca0+-MgO/S102) showing significant increase above a 7 slag basicity. Charge mix basicity of 0.2 was found to give maximum Mn and Si recoveries. Increasing or decreasing charge basicty from 0 2 resulted in lower metallic yield and Mn and Si recoveries. This has been explained with liquidus calculations of final slags obtained at those charge mix basicities. Addition of CaF2 during holding time i.e. time given after complete melting of charge mix was found to be beneficial. The optimum amount of CaF2 was 4% of WMNR+Mn ore blend, which gave rise to maximum Mn and Si recoveries and metallic yield. Further addition of CaF2 (4%) produced a high basicity slag (basicity =a 83) having very high liquidus leading to decrease in metallic yield and Mn and Si recoveries

Sorption characteristics of aqueous copper onto residue generated in ammoniacal leaching of manganese nodules

The present paper reports the studies on copper removal from its aqueous solution using residue generated in the process of reduction roast- ammonia leaching of manganese nodules. The leached residue was washed with water to remove the entrapped liquor containing metals from leaching operation, dried and used for adsorption of aqueous Cu(II) under varying experimental conditions. The particle size analyses of manganese nodule residue (wMNR) showed very fine particles with mean diameters (d50) of 17.8 µm. The BET surface area of wMNR was found to be 66.7 m2g-1. Adsorption studies of copper aqueous solution by batch equilibrium method indicated that the equilibrium was attained within 4 h. The percentage of Cu(II) adsorption increased with increase of leached residue dose but decreased with increase of initial Cu(II) concentrations. The adsorption was found to be dependent on initial pH of Cu(II) solution, which increased with increase in initial pH. During uptake of Cu(II), various metal ions, especially Mn and Fe, were found to be released from leached residue, which decreased with increase of pH. Pseudo second-order kinetics was applicable for the Cu(II) adsorption. Adsorption data were satisfactorily fitted to the Langmuir isotherms. The maximum adsorption capacity determined by Langmuir isotherm was found to be 26.95 mg g-1 at pH 5.5 and 303 K. Thus the leach residue found to be useful for removal of heavy metal like copper from the industrial effluent

Oxidative decolorization of methylene blue by leached sea-nodule residues generated by the reductionroasting ammoniacal leaching process

The leached residue, generated after selective extraction of Cu, Ni and Co by reductive-roasting ammoniacal leaching of sea nodules, was characterized by various physicochemical methods. The finely divided residue, containing mainly manganese carbonate/silicates and manganese(III,IV) (hydr)oxides along with iron oxides, showed a lower surface area (66.3 m2g− 1)than that of the parent sea nodule (130 m2g− 1). The catalytic efficiency of water-washed sea nodule residue (WSNR) was evaluated taking oxidative decolorization of methylene blue (MB) as the test reaction. The extent of decolorization was decreased with increase in pH but increased in the presence of H2O2 or NaCl. Decolorization of MB occurred in two consecutive steps; the rate constant of the first step was ∼ 10 times higher than that of the second step. The formation of a surface precursor complex between WSNR and MB at a rate-limiting step, followed by electron transfer from MB to the active metal centre of WSNR and release of product(s), was proposed as the ecolorization process

Chloridizing Roasting of Spent NdFeB Magnet Using Ammonium Chloride

The thermogravimetry is a useful tool to understand the roasting behavior of ores and minerals. Roasting of spent rare earth magnet (NdFeB) has evolved as attractive method for recycling of rare earth elements (REE) to conserve their scarce resources. We studied the chloridizing roasting of spent magnets of wind turbines with an objective to selectively convert the REE into water soluble chlorides. TG-DTA of NdFeB powder shows the commence of oxidation above 300°C. Further TG-DTA studies of NdFeB-NH4Cl mixture corroborated with thermodynamic calculations indicates 300°C as suitable temperature for chloridizing roasting process to obtain the NdCl3 and Fe2O3

Thermochemical Simulation, Thermogravimetry and Roasting Studies for Selective Sulfation of Copper in Flash Smelter Dust.

The thermal studies are a useful tool to understand the conversion of chalcopyrite to copper sulfate. We carried out thermochemical simulation in combination with thermogravimetric studies to understand the sulfation behavior of copper and iron in a copper smelter dust sample and to predict suitable roasting condition. Different oxide and sulfate phases of Cu and Fe forms as function of temperature. A temperature range of 150-1000°C was applied; however, a 550-650°C was found suitable for selective sulfation of copper. Further tests in a tube furnace at 600°C for three hours ensured 96% Cu sulfation and only 2.1% Fe sulfation

Making standard grade FeSiMn alloy by blending of different low grade materials.

NML has developed a process for extraction of Cu, Ni, & Co from sea nodules by reduction roast - ammonia leaching - solvent extraction - electrowinning route on pilot scale. This process generates leach liquor (Cu, Ni & Co) and a fine residue having low Mn/Fe ratio (not suitable for direct silicomanganese smelting). The utilization of huge quantity of leached residue is therefore, a matter of great concern. Development of another process of direct smelting of sea nodules in arc furnace to separate Cu, Ni & Co in alloy is being carried out which generates Mn rich slag with high Mn/Fe ratio. In this endeavor these two low Mn containing materials are blended to have suitable Mn/Fe ratio and smelted in 50 KVA DC arc furnace to produce standard grade FeSiMn alloy