Design and Development of Domestic Solar Dryer with Comparative Analysis of Nutritional Aspect of Dried Raisins

Solar dryer technology is simple and can be implemented by households and small communities due to its simplicity. The suitable design of the absorber/collector is very vital for any solar drying system as the collector efficiency plays a key role in determining the overall system drying efficiency. To study the practical applicability of a developed solar dryer, grapes were dried in the drying chamber of a designed and developed solar dryer and for comparison, in open sunlight. Faster drying was noted for the grapes dried in the unit. The study on nutritional aspects indicated that solar drying process retained the major nutritional components like total sugars, total proteins and total lipids in raisins. The comparison between the solar dried raisins and open sun dried ones showed a higher ash content of 2.71% with solar dried ones and 1.95% in case of open sun dried raisins. The quantity of MUFA content was also affected by the varying drying practices implemented with 10.95% and 7.12% MUFA in solar dried and open sun dried raisins respectively. The drying technique also affects the bacterial load on raisins as observed in our current study with negligible bacterial growth on on solar dried raisins compared to open dried ones

Dye adsorption using low cost carbon adsorbent from agrowaste-pearl millet cob husk

35-43Activated carbon (MHAC) has been derived from the millet cob husk in a single step activation at a temperature of 600oC, impregnation ratio of 2:1 and residence time of 120 min. The Brunauer–Emmett–Teller (BET) surface area of the MHAC is 1342 m2/g and the scanning electron microscopy (SEM) images and Fourier-transform infrared spectroscopy (FT-IR) are similar to commercial activated carbon. The dye removal performance of the generated carbon has been investigated using methylene blue (MB) using following parameters; contact time, initial concentration of MB, pH and temperature. Langmuir, Freundlich, Temkin and Dubinin–Radushkevich (D-R) adsorption isotherms and three kinetic models have been studied. The adsorption equilibrium data is best fitted to Langmuir isotherm with R2 value of 0.972 .The adsorption kinetics show that pseudo-second-order kinetic model fits better with the experimental data of MB adsorption by MHAC than pseudo-first-order kinetic model. Regeneration of the carbon has been carried out for five cycles and 85.34 % MB could be adsorbed by the spent carbon, after fifth cycle

Dye adsorption using low cost carbon adsorbent from agrowaste-pearl millet cob husk

Activated carbon (MHAC) has been derived from the millet cob husk in a single step activation at a temperature of 600oC, impregnation ratio of 2:1 and residence time of 120 min. The Brunauer–Emmett–Teller (BET) surface area of the MHAC is 1342 m2/g and the scanning electron microscopy (SEM) images and Fourier-transform infrared spectroscopy (FT-IR) are similar to commercial activated carbon. The dye removal performance of the generated carbon has been investigated using methylene blue (MB) using following parameters; contact time, initial concentration of MB, pH and temperature. Langmuir, Freundlich, Temkin and Dubinin–Radushkevich (D-R) adsorption isotherms and three kinetic models have been studied. The adsorption equilibrium data is best fitted to Langmuir isotherm with R2 value of 0.972 .The adsorption kinetics show that pseudo-second-order kinetic model fits better with the experimental data of MB adsorption by MHAC than pseudo-first-order kinetic model. Regeneration of the carbon has been carried out for five cycles and 85.34 % MB could be adsorbed by the spent carbon, after fifth cycle

Fixed-bed adsorption of Reactive Orange 84 dye onto activated carbon prepared from empty cotton flower agro-waste

The adsorption potential of empty cotton flower agro-residue based activated carbon (CFAC) to adsorb Reactive Orange 84 (RO84) dye from aqueous solution was studied using packed-bed adsorption column. The breakthrough curve characteristics were highly influenced by process variables like influent flowrate, inlet RO84 dye concentration and CFAC bed height. The findings indicated that higher value of dye concentration and bed height were favorable but high influent flowrates was unfavorable for adsorptive removal of RO84 dye. The maximum adsorption capacity of column was found to be about 720 mg of RO84 per 4.67 g of CFAC adsorbent for initial concentration, flowrate and bed height of 200 mg L−1, 15 mL min−1 and 5 cm, respectively. Thomas, Yoon–Nelson and Bed Depth Service Time (BDST) models were applied to calculate kinetic parameters of the laboratory fixed-bed adsorption column. Based on error analyses, Thomas model and BDST model fitted well than Yoon–Nelson model. The study concluded that CFAC is an effective adsorbent for adsorption of RO84 dye using fixed-bed adsorption column. Keywords: Empty cotton flower waste, Reactive Orange 84, Fixed-bed adsorption, Breakthrough curve, Kinetic model

Co-production of syngas and potassium-based fertilizer by solar-driven thermochemical conversion of crop residues

We report on the thermochemical conversion of inedible crop residues using concentrated solar energy as the source of high-temperature process heat. Experiments were performed using a 5 kWth solar packed-bed reactor exposed to radiative fluxes up to 1788 suns. The waste biomass feedstock consisted of unprocessed batches of cotton boll, soybean husk, and black mustard husk and straw, which were pyrolysed and steam-based gasified at nominal temperatures in the range 879–1266 °C, yielding high-quality syngas with molar ratios in the range H2:CO = 1.43–3.25, CO2:CO = 0.28–1.40, and CH4:CO = 0.03–0.28. The solar-to-fuel energy conversion efficiency, defined as the ratio of the heating value of the syngas produced to the solar radiative energy input and the heating value of the feedstock, reached 18%. The heating value of the feedstock was solar-upgraded by 7%, thus outperforming autothermal gasification that typically downgrades by at least 15%. The ash contained 23% potassium. The solar-driven thermochemical process offers a sustainable and efficient path for the conversion of agricultural wastes into valuable fuels and soil fertilizers.ISSN:0378-382

Solar Photothermochemical Reaction and Supercritical CO₂ Work up for a Fully Green Process of Preparation of Pure <i>p</i>‑Nitrobenzyl Bromide

It has been reported by us recently that <i>p</i>-nitrobenzyl bromide (PNBBr) can be synthesized from <i>p</i>-nitrotoluene (PNT) in high isolated yield with respect to available bromine in 2:1 Br^––BrO₃^– employed as brominating reagent. The reaction was conducted in ethylene dichloride (EDC) and the substrate was taken in excess to suppress dibromo impurity formation. The product was “cold crystallized” from the reaction mass and the mother liquor was recycled in the subsequent batch thereby eliminating organic discharge. The present work attempts to further advance the synthesis of this commercially important molecule employed in protection–deprotection strategies. Herein its successful synthesis employing neat substrate and solar radiation as the sole energy source to drive this photothermochemical reaction is reported. Further, 100% pure PNBBr could be isolated from the solid reaction mass in 87% yield by leaching out the excess substrate through supercritical CO₂ (Sc-CO₂) extraction. The reaction was therefore accomplished cleanly in all respects and with low carbon footprint