Influence by varying organic matter content and forms in suspended particulate matter: impacts on the adsorption of tetracycline and norfloxacin

Antibiotics are commonly detected in natural waters. The organic matter (OM) in suspended particulate matter (SPM) has a critical impact on the adsorption of antibiotics in water. We investigated the contribution of OM content and form to the adsorption of tetracycline (TC) and norfloxacin (NOR) in the SPM of Taihu Lake. To change the content and form of OM in SPM, the samples were subjected to pyrolysis at 505 ˚C and oxidization with H2O2, respectively. Combustion almost completely removed OM, while oxidation removed most of the OM and transformed the remaining OM. Regardless of whether the OM changed or not, the adsorption of NOR and TC by SPM was more in line with the pseudo-second-order kinetic model instead of pseudo-first-order. The fitting of the intraparticle diffusion model showed that the removal of OM had a certain degree of change in the adsorption process. The isothermal adsorption of TC in all samples was more in line with the Temkin model. The isothermal adsorption of NOR in the oxidized sample conformed to the Temkin model, while it conformed to the Langmuir model in the original sample and the sample removed OM via combustion. The adsorption capacity of SPM with almost complete removal of OM significantly decreased, while conversely, the adsorption capacity of SPM after oxidation increased. This indicates that both the content and form of OM affect the adsorption of antibiotics by SPM, and the form of OM has a greater impact. The contribution of OM to NOR adsorption was greater than that of TC. In conclusion, the results verify the importance of OM in adsorbing antibiotics onto SPM, which may provide basic data for antibiotic migration in surface water.

Optimization of hydrothermal synthesis of hydroxyapatite from chicken eggshell waste for effective adsorption of aqueous Pb(II)

Proper disposal of the millions of tons of eggshell waste generated around the world every year is a significant environmental challenge. However, eggshell waste can be converted into new materials that may be useful for a wide range of applications. In this study, four methods, including the conventional subcritical hydrothermal method (CSHM), microwave-assisted subcritical hydrothermal method (MSHM), conventional low-temperature hydrothermal method (CLHM), and ultrasonic-assisted low-temperature hydrothermal method (ULHM) were used to convert eggshell waste into hydroxyapatite (HAP). For each hydrothermal method, increasing the reaction temperature increased production efficiency and improved the degree of crystallinity of HAP. X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area analysis, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to characterize the preferred eggshell-derived HAP, which was produced by the MSHM at 180 °C in a period of only 1 h. For the MSHM, the HAP yield was 75.3%, the degree of HAP crystallinity was as high as 0.78, and pure, rod-like, nano-sized HAP particles with high specific surface area were produced. For the preferred HAP produced by the MSHM, the adsorption capacity of Pb²⁺and pH were positively related in the range of pH 1-6. Consequently, the HAP produced by the MSHM showed relatively high maximum adsorption (q_m= 505.05 mg/g) of Pb²⁺ in aqueous solution. The adsorption process followed a pseudo-second-order reaction model, and the equilibrium adsorption was well fit by the Langmuir model.

Adsorption behaviours and transfer simulation of levofloxacin in silty clay

Fluoroquinolone antibiotics in soil can cause serious antibiotic pollution. Adsorption is the main factor that influences their destination and transport of antibiotics. Therefore, research on the behaviour of antibiotics once they reach the soil environment is meaningful to design appropriate measures to reduce their potential risks. This research took levofloxacin (LVFX) as the research object and used a static adsorption experiment to study the adsorption behaviour of the vadose zone of silty clay on the North China Plain. The results showed that LVFX had high retention in silty clay, with an average adsorption ratio of more than 90%. Adsorption of LVFX on silty clay reached equilibrium in 24 h with an adsorption amount of 93.5 mg/kg at an initial LVFX concentration of 10 mg/L. Acidity, cations and soil organic matter could affect the adsorption of LVFX, with adsorption variation ratio of 3.3%, 3.4% and 0.6%, respectively. In addition, numerical simulation with Hydrus-1D was utilized, and the results show that LVFX may infiltrate into underground water through silty clay after 28 days and completely penetrate in 100 days.

Insight on adsorption of cellulase on wet ground corncob residues and its evaluation by multivariate linear analysis

Understanding the adsorption behavior and the interaction between substrates and enzymes are critical to improving enzymatic hydrolysis efficiency and reducing bioconversion cost. Herein, the adsorption of cellulase on wet ground corncob residues was studied, and the effects of main characteristics of wet ground corncob residues on adsorption capacity were quantitatively analyzed with the combination of principal component analysis and multiple linear regression models. The results showed that the adsorption of cellulase on wet ground corncob residues was fitted well with Langmuir isotherm adsorption and pseudo second-order kinetics model, the adsorption rate and adsorption capacity were greatly enhanced with increasing grinding time; the multiple linear regression models describing the relationship between main characteristics of corncob residues and adsorption capacity to cellulase were established; the significance of these characteristics were in the following order: average particle size, crystallinity index, specific surface area, surface lignin concentration, water retention value, and surface charge density.

Transformations of 2-line ferrihydrite and its effect on cadmium adsorption

In this study, 2LFh was synthesized, and the effects of 2LFh synthesis in the laboratory as well as its synthetic products' mineral crystal phase changes during high temperature aging process caused by Ca²⁺, Mg²⁺, and Cl^- were also studied. In addition, the Cd²⁺ adsorption effects of the products above with different pH values and different Cd²⁺ concentrations were studied in this experiment. The results showed that the existence of Ca²⁺ had no significant effect on the synthesis and aging of 2LFh. However, in the presence of Mg²⁺ and Cl^-, the akaganeite could be found in the synthetic material, and with the increase of the ion concentration, the crystallinity of the formed akaganeite was higher. And akaganeite had a significant inhibitory effect on the aging of 2LFh, causing the Cd²⁺adsorption effect of 2LFh after aging was better than that of pure 2LFh. The adsorption and removal rates of Cd²⁺ in Fh2 series and Fh2-200 series were increased with the increase of initial concentration. With the increase of pH, the adsorption capacity and removal rate were increased, and the removal rate reached nearly 100% when pH value is ranging from 10 to 11. The isothermal adsorption experiment showed that the isothermal adsorption process of Cd²⁺ in Fh2 series and Fh2-200 series was in accordance with the Freundlich model. The affinity coefficient (Kf) of the Freundlich model of Fh2-200 series arranged in descending order is Fh2-200-Mgs> Fh2-200-Cas> Fh2-200s, showing that the Cd²⁺ adsorption capacity of Fh2-200 was relatively weak, while that of Fh2-200-Ca series and Fh2-200-Mg series was relatively strong, which was confirmed by the experimental results.

Complexation of synthetic CDM-AM copolymer with natamycin and carbendazim to improve solubility and fungicidal activity

The β-cyclodextrin-acrylamide (CDM-AM) copolymer was prepared from acrylamide and β-CD maleate (CDM) using K2S2O8 as initiator. The effects of the CDM-AM copolymer on the solubility and fungicidal activity of natamycin (NM) and carbendazim (MBC) were investigated. The stability constant of NM·CDM-AM and MBC·CDM-AM complexes at 303 K were of 10,725.45 M(-1) and 3000.89 M(-1), respectively. The complexes were characterized using phase solubility diagrams, NMR spectra and FT-IR spectra. The analysis of the biological activities of these two complexes indicated that they possessed enhancing fungicidal activities compared to NM and MBC alone.