Effects of aqueous phase circulation and catalysts on hydrothermal liquefaction (HTL) of penicillin residue (PR): Characteristics of the aqueous phase, solid residue and bio oil

Hydrothermal liquefaction (HTL) is a promising thermochemical technology for the treatment of hazardous wastes such as penicillin residue (PR). For the treatment of aqueous waste produced by PR in the HTL process, aqueous phase circulation is an attractive solution, both environmentally and economically. The present study shows that aqueous phase circulation can promote the transfer of organic matter from the aqueous phase to bio-oil. The content of organic acids and alcohols in the aqueous phase decreased significantly, and the bio-oil yield and energy recovery efficiency also increased. Under non-catalytic conditions, the bio-oil yield increased from 26.09 wt% to 33.72 wt%. The use of Na₂CO₃ as a catalyst further improved the bio-oil yield. After a single aqueous phase circulation, the bio-oil yield increased to 34.63 wt%, and the energy recovery efficiency increased to 66.94%. Under catalytic hydrothermal conditions, the content of organic acids in the bio-oil was reduced using aqueous phase circulations, which improved the quality of the bio-oil. At the same time, the Na₂CO₃ catalyst promoted the hydrolysis of PR to form small molecule organic matter, inhibited the formation of coke, and reduced the content of carbon, hydrogen and oxygen in the solid residue. An increase of cycle times led to excessive accumulation of Na₂CO₃, which had a negative impact on the yield of bio-oil. Nitrogen-containing compounds in the bio-oil increased to a certain extent, which renders it necessary to consider denitrification treatments in the future. The work provides a useful reference for further research on the preparation of high quality bio-oil by PR hydrothermal liquefaction.

Assessing the stability in dry mycelial fertilizer of Penicillium chrysogenum as soil amendment via fluorescence excitation-emission matrix spectra: organic matter's transformation and maturity

Utilization as dry mycelial fertilizer (DMF) produced from penicillin fermentation fungi mycelium (PFFM) with an acid-heating pretreatment is a potential way. To study the transformation and stability of water-extractable organic matter in DMF-amended soil via fluorescence regional integration (FRI) of fluorescence excitation-emission matrix (EEM), a soil experiment in pot was carried out. The results showed that residual penicillin (about 32 mg/kg) was almost degraded in the first 5 days, indicating that the drug pollution was in control. The pH value, DOC, DON, and DOC/DON presented a classical profile, but germination index (GI) leveled off about 0.13 till day 13 in DMF-12% treatment due to the severe phytotoxicity. The addition of DMF significantly increased the soil microbial populations in contrast to the CON treatment. The EEM showed that the protein-like and microbial byproduct-like matters vanished on the 25th and 33rd days, whereas the fulvic-like substances appeared on the 7th day. The humic-like substances existed in original samples but their content greatly enhanced finally. The FRI results showed that P _{V, n}/P _{III, n} reached the highest value of 1.84 on the 25th day, suggesting that DMF maintained stable in amended soil. Because of its consistency with the results of GI and DOC/DON, the EEM-FRI has a potential to evaluate the stability of DMF in soil.