Biswapriya Das

Pilot scale study on steam explosion and mass balance for higher sugar recovery from rice straw.

Pretreatment of rice straw on pilot scale steam explosion has been attempted to achieve maximum sugar recovery. Three different reaction media viz. water, sulfuric acid and phosphoric acid (0.5%, w/w) were explored for pretreatment by varying operating temperature (160, 180 and 200°C) and reaction time (5 and 10min). Using water and 0.5% SA showed almost similar sugar recovery (∼87%) at 200 and 180°C respectively. However, detailed studies showed that the former caused higher production of oligomeric sugars (13.56g/L) than the later (3.34g/L). Monomeric sugar, followed the reverse trend (7.83 and 11.62g/L respectively). Higher oligomers have a pronounced effect in reducing enzymatic sugar yield as observed in case of water. Mass balance studies for water and SA assisted SE gave total saccharification yield as 81.8% and 77.1% respectively. However, techno-economical viability will have a trade-off between these advantages and disadvantages offered by the pretreatment medium.

Electro-biocatalytic treatment of petroleum refinery wastewater using microbial fuel cell (MFC) in continuous mode operation

Refinery wastewater (RW) treatment in microbial fuel cell (MFC) was studied in batch mode operation followed by continuous mode operation with 8h and 16h hydraulic retention time (HRT). The MFC performance was evaluated in terms of power density, organics removal, specific contaminants (oil & grease, phenol and sulfide) removal and energy conversion efficiency with respect to operation mode. Higher power density of 225±1.4mW/m2 was observed during continuous mode operation with 16h HRT along with a substrate degradation of 84.4±0.8% including the 95±0.6 of oil content. The columbic efficiency during this operation was about 2±0.8% and the projected power yield was 340±20kWh/kg CODR/day. Batch mode operation also showed good substrate degradation (81±1.8%) but took longer HRT which resulted in significantly low substrate degradation rate (0.036±0.002kgCODR/m3-day) over continuous mode operation (1.05±0.01kgCODR/m3-day). Overall, current study depicted the possibility of utilizing RW as substrate in MFC for power generation along with its treatment.

Evaluation of recalcitrant features impacting enzymatic saccharification of diverse agricultural residues treated by steam explosion and dilute acid

Exploring agricultural biomass for biofuel production necessitates pretreatment as a prerequisite step. However, due the variability in recalcitrance among biomasses, choosing an optimum pretreatment methodology suitable for multiple feedstocks is challenging. To assess which parameters of pretreated biomass may serve as useful indicators of potential subsequent enzymatic saccharification, an insight into the structural alteration during pretreatment and its impact on the downstream process is essential. In this study, two pretreatment methods, dilute acid (DA) and steam explosion (SE) have been employed on three different biomasses viz. rice straw (RS), cotton stalk (CS) and mustard stalk (MS). The alteration in recalcitrant features of the pretreated residues was measured by chemical analysis, XRD, BET and FT-IR. FT-IR proved useful to measure the cellulose related properties viz. lateral order index (LOI) and hydrogen bond index (HBI) besides lignin related features, i.e. cross-linked lignin (CLL), lignin/cellulose (L/C) and syringyl/guaiacyl (S/G) ratio. The results show that S/G ratio, specific surface area and HBI of the pretreated residues had a positive correlation with enzymatic saccharification across different biomasses and pretreatment methodologies employed. On the other hand, lignin content, CLL, L/C ratio and LOI showed a negative correlation. However, the extent of xylan removal showed a positive correlation with the enzymatic saccharification only when a single pretreatment method was applied to different biomasses. The structure-activity correlation presented here would help to assess and predict the enzymatic saccharification while applying DA or SE pretreatment methods on different biomasses. This correlation could provide assistance in designing an optimum technology.

Evidence of antimagnetic rotation in an odd-odd nucleus: The case of 142Eu

The present work reported a conclusive evidence for anti-magnetic rotational (AMR) band in an odd-odd nucleus 142Eu. Parity of the states of a quadrupole sequence in 142Eu was firmly identified from polarization measurements using the Indian National Gamma Array and lifetimes of some of the states in the same structure were measured using the Doppler shift attenuation method. The decreasing trends of the deduced quadrupole transition strength B(E2) with spin, along with increasing J(2) / B(E2) values conclusively established the origin of these states as arising from Antimagnetic rotation. The results were well reproduced by numerical calculations within the framework of a semi-classical geometric model.