Effect of environmental factors on adsorption of ciprofloxacin from wastewater by microwave alkali modified fly ash.

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.

Effects of aging methods on the adsorption of antibiotics in wastewater by soybean straw biochar.

BACKGROUND: The environmental pollution and ecological risks caused by the widespread use of antibiotics have attracted attention in recent years. Biochar materials have a rich pore diameter and can effectively adsorb pollutants from wastewater. However, biochar will experience high temperatures, freezing and thawing in nature, affecting its physicochemical properties and adsorption capacity. Three types of aged biochar were prepared by artificial simulated aging using soybean straw as raw material. The aged biochar's elemental composition and functional group species were investigated by characterization analysis, and their adsorption kinetics and adsorption isotherms were studied. RESULTS: The specific surface area and pore size of the three aged biochars were lower than those of fresh biochars. The increased number of oxygen-containing functional groups of the aged biochars formed a water cluster interaction with norfloxacin (NOR), which was unfavorable to the adsorption of NOR. The adsorption mechanism of biochar on NOR comprises pore filling, electrostatic interaction, ion exchange and complexation. CONCLUSION: The adsorption of NOR on biochar before and after aging was spontaneous and was described by quasi-second kinetics and the Langmuir equation. Different aging methods influenced the physicochemical properties and adsorption performance of biochar, and the adsorption capacity of biochar was significantly reduced after aging. Therefore, the influence of climatic factors needs to be considered when using biochar to remove target pollutants. © 2023 Society of Chemical Industry.

Phosphorus adsorption characteristics and release risk in saline soils: a case study of Songnen Plain, China.

Introduction: The Songnen Plain is one of the three major saline-alkali areas in China, covering a vast area, where drought and overgrazing have exacerbated the salinization trend, and will have great potential for development if utilized rationally. Phosphorus, as one of important soil nutrients, plays a crucial role in plant growth. How to minimize its loss and migration has become a current research hotspot. The objective of the present study was to elucidate the adsorption properties of phosphorus in soils affected by salinization and to establish the correlation between the potential for phosphorus release and soil properties. Methods: A batch treatment test was conducted in this study using three soils with the various salinization degrees to examine the impact of environmental factors on the adsorption properties and potential release of phosphorus. Results and discussion: It was found that the maximum phosphorus adsorption by the three salinization soils in 0-360 minutes accounted for 86.8%-90.5% of the total adsorption capacity; the equilibrium adsorption capacity was: HS> MS> LS. In cases where the phosphorus level in the surrounding liquid is low, the three levels of salinized soils exhibited varying levels of phosphorus discharge, with the adsorbent acting as the origin of contaminants. The Pseudo-second-order model kinetics and Langmuir equation can well describe the adsorption process, and the adsorption process is spontaneous heat absorption with entropy increase. Increasing the pH led to an increase in the adsorption of phosphorus from the three salinized soils. Additionally, the adsorption was enhanced by introducing varying concentrations of Na+, Ca2+, and Al3+ to the background solution. The phosphorus eutrophication release risk (ERI) demonstrated a gradual decline as temperature increased. Correlation analysis revealed a noteworthy positive correlation between TN, TP, and ERI, as well as a significant negative correlation between CEC, K+, and ERI. Furthermore, there was a highly significant negative correlation between coarse silt and fine silt. Considering local climatic and environmental factors is crucial for controlling the adsorption capacity of phosphorus in various salinized soils, as it can unveil the mechanism of phosphorus adsorption and impact its migration and release risk.