Krishna Kanta Ghara

Production of pure potassium salts directly from sea bittern employing tartaric acid as a benign and recyclable K+ precipitant

The shortage of land and vulnerability to climate change expose the future production of potash from sea bittern through an evaporite route to greater risks. Potash recovery through selective extraction from bittern is an attractive alternative. Unfortunately, previous attempts in this direction have suffered from one drawback or another. The present study reports a viable scheme employing tartaric acid as a benign and recyclable K+ precipitant. The key steps in the scheme were (i) selective precipitation of potassium bitartrate in 81.2% yield with respect to magnesium tartrate used, (ii) decomposition of the bitartrate salt into potassium nitrate with regeneration of magnesium tartrate, and (iii) recovery of residual tartaric acid from K+-depleted bittern as calcium tartrate, from which tartaric acid was regenerated and reused. The process was made further viable through co-production of Epsom salt (0.30 t/t of KNO3) and ammonium sulphate (1.47 t/t of KNO3). Spent bittern, containing <50 ppm of tartaric acid, was the only effluent. The overall energy requirement for a 1 TPD KNO3 plant was estimated to be ca. 38.31 GJ per t of KNO3 production, along with the associated products, comparing reasonably with the computed figure of 34.80 GJ based on available data from a standard database. A simplified version of the above scheme yields a K–N–S compound fertilizer currently under evaluation.

Four-fold concentration of sucrose in sugarcane juice through energy efficient forward osmosis using sea bittern as draw solution

Clarified sugarcane juice (osmotic coefficient, φ, ∼1.01) was efficiently dewatered through the spontaneous process of Forward Osmosis (FO) employing sea bittern as draw solution. Sea bittern is the mother liquor that remains after recovery of common salt from seawater. It is either discarded to sea or evaporated to higher densities in solar salt pans for recovery of other marine chemicals such as bromine, Epsom salt, potash and magnesium chloride. Compared to seawater (φ = 0.905) which has limited potential as draw solution, the φ values of the sea bittern samples were in the range of 1.41 to 3.24, providing thereby a high osmotic drive. A polyamide thin film composite membrane was used in the study. With 1 bar applied pressure, room temperature operation, and 1 : 8 volume ratio of sugar cane juice to bittern (φ = 2.26; concentrations of main constituents (% w/v): Na+ = 2.83, K+ = 2.03, Mg2+ = 7.42, Cl− = 23.48, SO42− = 8.42), sucrose concentration in the juice was enhanced from 10.5% (w/v) to 40.6% (w/v) over 4 h, with average flux of 13 L m−2 h−1. Sucrose loss was <3%. Energy computations indicated a saving of 69 kg of bagasse per m3 of raw juice, assuming all process energy (steam/electricity) is derived from bagasse. Epsom salt of high purity was recovered from the spent draw solution upon chilling.

Development of high-performance supercapacitor electrode derived from sugar industry spent wash waste

This study aims at developing supercapacitor materials from sugar and distillery industry wastes, thereby mediating waste disposal problem through reuse. In a two-step process, biomethanated spent wash (BMSW) was acid treated to produce solid waste sludge and waste water with significantly reduced total organic carbon (TOC) and biological oxygen demand (BOD) content. Further, waste sludge was directly calcined in presence of activating agent ZnCl2 in inert atmosphere resulting in high surface area (730-900m2g-1) carbon of unique hexagonal morphology. Present technique resulted in achieving two-faceted target of liquid-solid waste remediation and production of high-performance carbon material. The resulted high surface area carbon was tested in both three and two electrode systems. Electrochemical tests viz. cyclic voltammetry, galvanostatic charge-discharge and impedance measurement were carried out in aqueous KOH electrolyte yielding specific capacitance as high as 120Fg-1, whereas all solid supercapacitor devised using PVA/H3PO4 polyelectrolyte showed stable capacitance of 105Fg-1 at 0.2Ag-1. The presence of transition metal particles and hetero-atoms on carbon surface were confirmed by XPS, EDX and TEM analysis which enhanced the conductivity and imparted pseudocapacitance to some extent into the working electrode. The present study successfully demonstrated production of high-performance electrode material from dirtiest wastewater making process green, sustainable and economically viable.

Evaluation of Fertilizer Potential of Different K Compounds Prepared Utilizing Sea Bittern as Feed Stock

Aim: Many countries import potassic fertilizers due to dearth of K-mineral deposits. Therefore processes to obtain K-nutrient sources from sea bittern were developed by our Institute. The present investigation evaluated the fertilizer potential of three different sea bittern-derived (SBD) potassium forms developed viz., potassium schoenite, potassium nitrate and potassium ammonium sulfate on maize productivity in two cropping seasons. Methods: The pot and field experiments consisted of four treatments, wherein the three K forms were applied at the recommended rate of 40 kg K2O ha−1 and were compared with commercially used sulfate of potash. The effect of these fertilizers on different parameters of plant and soil were evaluated. Results: The application of SBD-potassic fertilizers led to enhancement in growth, productivity and quality of maize which related well with higher photosynthesis, nutrient uptake and soil quality parameters. On an average all the three forms of sea bittern-derived potash enhanced yield of maize over control by 22.3 and 23.8%, respectively, in pot and field trials. The best performance was under SBD-KNO3, which also recorded the highest benefit: cost ratio of 1.76. Conclusion: The K-fertilizers derived from sea-bittern—a waste product of salt industry—can thus be economically used to improve crop production sustainably.