Pratyush Maiti

Kappaphycus alvarezii as a source of bioethanol.

The present study describes production of bio-ethanol from fresh red alga, Kappaphycus alvarezii. It was crushed to expel sap--a biofertilizer--while residual biomass was saccharified at 100 °C in 0.9 N H2SO4. The hydrolysate was repeatedly treated with additional granules to achieve desired reducing sugar concentration. The best yields for saccharification, inclusive of sugar loss in residue, were 26.2% and 30.6% (w/w) at laboratory (250 g) and bench (16 kg) scales, respectively. The hydrolysate was neutralized with lime and the filtrate was desalted by electrodialysis. Saccharomyces cerevisiae (NCIM 3523) was used for ethanol production from this non-traditional bio-resource. Fermentation at laboratory and bench scales converted ca. 80% of reducing sugar into ethanol in near quantitative selectivity. A petrol vehicle was successfully run with E10 gasoline made from the seaweed-based ethanol. Co-production of ethanol and bio-fertilizer from this seaweed may emerge as a promising alternative to land-based bio-ethanol.

Fuel intermediates, agricultural nutrients and pure water from Kappaphycus alvarezii seaweed

The present work reports a standalone integrated scheme for the production of 5-hydroxymethyl furfural (HMF) and potassium sulphate (K2SO4) from granular biomass rich in the sulphated polysaccharide, κ-carrageenan. Fresh Kappaphycus alvarezii seaweed was crushed to expel the juice rich in KCl (0.7 m3 t−1 of fresh seaweed) and granular biomass (0.04 t dry weight per t of fresh seaweed). The latter yielded κ-carrageenan through seawater extraction. HMF was derived from this phycocolloid through reaction with Mg(HSO4)2 acid catalyst and isolated in pure form. Galactose was a co-product which remained in the aqueous phase. The aqueous phase was recycled up to 10 times by maintaining a constant acid strength, and utilized thereafter for the recovery of K2SO4. Selective crystallization of K2SO4 was guided by the phase diagram and use was made of a part of the seaweed juice in this process. The spent aqueous phase rich in galactose was subjected to further reaction with HCl obtainable through bipolar electro-dialysis (ED) of seaweed juice. The reaction yielded levulinic acid (LA) and formic acid (FA) in nearly equal proportions. The processing of 1 t of granular biomass was computed to require 30.15 GJ of energy and would yield 0.18 t HMF, 0.056 t LA, 0.020 t FA, 0.27 t K2SO4, and 5.77 m3 pure water. The process energy requirement for the scheme can be met from additional supplies of granule (3.35 t). Combustion/gasification of this biomass would yield additionally 0.74 t glaserite fertilizer and the required amount of H2SO4 for Mg(HSO4)2 preparation.

Surfactant-induced coagulation of agarose from aqueous extract of Gracilaria dura seaweed as an energy-efficient alternative to the conventional freeze–thaw process

Surfactant-induced coagulation of agarose from alkali-treated Gracilaria dura seaweed extract (SE) is reported. The new approach, which was suitable for linear galactans with low sulphate content is an alternative to the traditional energy intensive process of “freeze–thaw” cycles employed for product isolation from the extract. Only nonionic surfactants were effective, and detailed studies were undertaken with octyl phenol ethoxylate (Triton X-100). The coagulated product was successively washed with water and water–isopropyl alcohol (IPA) to yield a fine powder of agarose in 13–15% yield (with respect to dry biomass). The product exhibited excellent properties [sulphate content: 0.2% w/w; degree of electro-endosmosis: 0.13; gel strength: 2200 g cm−2 (1% gel, w/v); and gelling temperature: 35 ± 1 °C] essential for demanding molecular biology applications, and the desired gel electrophoretic separation of DNA and RNA was demonstrated. It was further confirmed that there was no degradation of nucleic acids in the gel. The agarose-depleted extract, along with water used for washings, was subjected to reverse osmosis for recovering the surfactant in concentrated form for its subsequent reuse. Energy savings from the improved process were assessed.

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 1u2006:u20068 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.

Syntheses, characterization and crystal structures of potassium and barium complexes of a Schiff base ligand with different anions

AbstractNew pseudopolymorph of a O,N,N’-donor hydrazone ligand, 2-pyridylcarboxaldehyde isonicotinoylhydrazone (L) and its discrete complexes with K+ and Ba2+ have been reported. L forms isostructural dinuclear complexes with K+ when bromide and iodide were employed as counter anions. However, a monomeric complex in the case of Ba2+ with existence of coordinated as well as lattice perchlorate counter anions was observed. All compounds were characterized by single crystal X-ray analysis and other physicochemical techniques. Structural analysis and spectral features of all compounds are described in detail.n Graphical AbstractNew psuedopolymorpic form of the schiiff base ligand O,N,N-donor hydrazone ligand(2-pyridylcarboxaldehyde isonicotinoylhydrazone) (L) and the their complexes with alkali and alkaline earth metal have been investigated by various physico-chemical techniques such as FTIR, TGA, PXRD and solid state absorption spectra including X-ray crystallography. L formed isostructural binuclear complexes with K+ when bromide and iodide were employed as counter anion, whereas, a mononuclear complex with Ba2+ having coordinated as well as uncoordinated perchlorate counter anion.

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.