Introduction: Composting is a highly effective method for managing the growing quantity of agricultural waste, promoting nutrient recycling, and advancing sustainable agriculture. However, the significant amounts of volatile inorganic compounds (VICs) and volatile organic compounds (VOCs) generated during the composting process cannot be ignored due to their serious ecological environmental hazards and detrimental impact on human health. The types and pathways of VICs and VOCs produced during the composting process remain not well understood.Methods: In this study, we investigated the VOCs produced during chicken manure and straw composting using gas chromatography–mass spectrometry (GC/MS). We performed qualitative and quantitative analyses of VOCs in composting emissions gases and their correlation with odor.Results: Our results showed that 44 VOCs were detected during composting, including 4 oxidation-containing compounds, 2 sulfur-containing organics, 5 alkanes, 19 halogenated compounds, and 14 aromatic compounds. Aromatic compounds were found to be the main component of VOCs, accounting for 59.14% of the total content. The highest VOC content was found in the pre-composting period, and the highest emitting VOC was p-Isopropyl Toluene, which reached 7870.50 μg/m³. We identified eight substances that were highly correlated with odor concentration (p < 0.01) and are the main odor-causing substances that need to be monitored and controlled.Discussion: Our study provides important insights into the transformation of volatile gases during the composting process. It highlights the need for proper management practices to control VOCs emissions and reduce their environmental impact.

Antibiotics, as emerging persistent pollutants, pose significant threats to human health. The effective and low-cost removal of ciprofloxacin (CIP) from wastewater has become an important research focus. In this study, fly ash (FA) was used as the raw material, and modified fly ash (MFA) was prepared by varying microwave power, alkali concentration, and immersion time to investigate its adsorption characteristics for CIP. Results showed that the optimal preparation conditions for MFA with the most effective adsorption of CIP, using the Box-Behnken response surface methodology, were a microwave power of 480 W, an alkali concentration of 1.5 mol/L, and a modification time of 3 h. Scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction analyses revealed that after modification, the glassy structure of FA is destroyed, the specific surface area is increased, and obvious hydroxyl O–H absorption peaks appear. Both FA and MFA exhibited adsorption processes for CIP that conformed to pseudo-second-order kinetics and the Langmuir equation. Maximum adsorption of CIP (9.61 and 12.67 mg/g) was achieved at pH = 6. With increasing temperature, the adsorption capacity of both FA and MFA for CIP decreased, indicating an exothermic process. The adsorption capacity of CIP decreased with increasing ion concentration, with the impact order of ions being Al³⁺ > Ca²⁺ > Na⁺. The results show that pore filling, electrostatic interaction, ion exchange and complexation are the main ways of CIP adsorption by FA. Microwave alkali modified fly ash is an economical and efficient adsorbent for CIP removal in water, realizing the purpose of “treating waste with waste”. This study provides a scientific basis for controlling CIP treatment in wastewater.

In this paper, composting technology was used to treat agricultural waste chicken manure. The dynamic changes of the relative amount, chemical, optical and thermal properties of humic acid during the composting process were systematically studied. The results showed that the relative amount of humic acid increased from 5.46% to 8.36% with the ratio of H/C decreased and the condensation degree of humic acid molecule increased. In the infrared spectrum of humic acid, the integral area ratio of aromatic absorption peak to aliphatic absorption peak decreased from 0.51 to 0.14, and the lgK also decreased, it indicated that composting treatment was beneficial to the decomposition of simple compounds and the formation of complex organic matter in chicken manure. However, after 30 days of composting treatment, the lgK decreased to 0.85, which was still higher than that in farming soil, i.e., the molecular structure of humic acid in chicken manure treated by composting still has potential for further stabilization. Differential thermal analysis showed that the Peak Exothermic Temperature and weight loss all increased with the increase of composting time of chicken manure, which indicates that the molecular structure of humic acid in chicken manure became more complex and the degree of humification was obvious. Therefore, composting treatment can not only increase the relative amount of humic acid in organic materials but also improve the quality of humic acid.

The recycling of fruit peel resources is a current research hotspot. This study screened and configured a composite extractant consisting of peel and chemical extractant through extraction experiments and explored the heavy metals(HMs) release effect. The results showed that citrus reticulata(CR), citrullus lanatus (CL), 0.16 mol·L^-1 nitrilotriacetic acid(NTA) with 0.04 mol·L^-1 oxalic acid(NO5), and 0.12 mol·L^-1NTA with 0.08 mol·L^-1tartaric acid(NT4) had the strongest extraction ability. After the cross-combination was optimized, CR-NO5 (1:50, 6 h, 35 °C) and CL-NT4 (1:50, 36 h, 45 °C) had the highest extraction rates for Cd and Zn, which were 92.6 % and 98.4 %, respectively. The CL series increased the nutrient content of sludge (157.75-177.88 g·kg^-1). The four combined extractants increased the proportion of soluble components of HMs in sludge (14-36 %). Therefore, the combined leaching agent will provide a valuable reference for the harmless treatment of HMs in sludge and the resource utilization of peel waste.