Dispersed spherical shell-shaped palygorskite/carbon/polyaniline composites with advanced microwave absorption performances

Colloid Mill-Assisted Ultrasonic-Fractional Centrifugal Purification of Low-Grade Attapulgite and Its Modification for Adsorption of Congo Red

Attapulgite (APT) is widely used in wastewater treatment due to its exceptional adsorption and colloidal properties, as well as its cost-effectiveness and eco-friendliness. However, low-grade APT generally limits its performance. Here, a colloid mill-assisted ultrasonic-fractional centrifugal purification method was developed to refine low-grade APT. This process successfully separated and removed impurity minerals such as quartz and dolomite from the raw ore, resulting in a refined APT purity increase from 16.9% to 60% with a specific surface area of 135.5 m2∙g-1. Further modifying of the refined APT was carried out through the hydrothermal method using varying dosages of cetyltrimethylammonium chloride (CTAC), resulting in the production of four different APT adsorbents denoted as QAPT-n (n = CTAC mole number) ranging from 0.5 to 5 mmol. Using Congo red (CR) as the target pollutant, the QAPT-5 sample exhibited the best adsorption capacity with the maximum quantity of 1652.2 mg∙g-1 in a neutral solution at 30 °C due to the highest surface charge (zeta potential = 8.25 mV). Moreover, the QAPT-5 pellets (~2.0 g adsorbent) shaped by the alginate-assisted molding method removed more than 96% of 200 mL aqueous solution containing 200 mg∙L-1 CR and maintained this efficiency in 10 adsorption-elution cycles, which exhibited the promising practical application.

Flocculation synergistic with nano zero-valent iron augmented attapulgite @ chitosan as Fenton-like catalyst for the treatment of landfill leachate

In this study, nano-zero-valent iron (NZVI) was added to attapulgite/chitosan and used as a catalyst in the heterogeneous Fenton process to degrade stabilized landfill leachate. Landfill leachate has serious environmental impacts due to the complexity and diversity of its pollutants. A magnetic catalyst (NZVI@PATP/CS) was prepared by a liquid-phase reduction method. The NZVI@PATP/CS were characterized by XRD, FTIR and SEM. The pH of leachate and the dosage of catalyst and H2O2 were changed to determine the best-operating conditions for the effective removal of chemical oxygen demand (COD) and total phosphorus(TP). To understand the adsorption degradation mechanism, the quenching experiments of free radicals were carried out. The results showed that the degradation rates of COD and TP were 66% and 92%, respectively, under the optimum pH value of 8, the dosage of H2O2 of 5 mL, and the dosage of the catalyst of 0.25 g for 60 min.

Nano-EMB-SP improves the solubility, foliar affinity, photostability and bioactivity of emamectin benzoate

BACKGROUND

Emamectin benzoate (EMB), a frequently used biopesticide, is poorly soluble in water, making it difficult to wet the leaf surface, is prone to degrade in sunlight and readily loses its bioactivity. Traditional methods such as organic solvent application, pH adjustment and addition of photoprotectants either increase the economic and environmental costs or barely achieve the desired goal. We hypothesized that nanotechnology could improve the solubility, foliar affinity, photostability and bioactivity of EMB. This research set out to prepare a nano-EMB solid powder (nano-EMB-SP) and test this hypothesis.

RESULTS

Nano-EMB-SP was prepared using a self-emulsifying method combined with carrier solidification. The mean particle size and Polydispersity index (PDI) of nano-EMB-SP were 14.64 nm and 0.24, respectively. A scanning electron microscopy image showed that EMB nanoparticles were mainly spherical or ellipsoidal in shape. Without organic solvent, the aqueous solubility of EMB in nano-EMB-SP was 4500 mg L^-1 , at least 14-fold that of the EMB soluble granule (EMB-SG), which is solubilized by pH adjustment. Excellent foliar affinity of EMB was achieved by nano-EMB-SP, which completely wet and penetrated the superhydrophobic surface of cabbage (Brassica oleracea L.) leaf. Without photoprotectants, up to 82% of EMB content can be protected from ultraviolet (UV) damage in nano-EMB-SP. The combined effects of excellent photostability and foliar affinity of nano-EMB-SP led to the bioactivity of EMB being almost unchanged before and after UV radiation.

CONCLUSION

Nano-EMB-SP is an eco-friendly and efficient way to improve the solubility, foliar affinity, photostability and bioactivity of EMB. This research provides a good approach to improving the efficacy of poorly soluble and UV-sensitive pesticides. © 2022 Society of Chemical Industry.

Synthesis of hollow core-shell ZnFe2O4@C nanospheres with excellent microwave absorption properties

The special hollow core-shell structure and excellent dielectric-magnetic loss synergy of composite materials are two crucial factors that have an important influence on the microwave absorption properties. In this study, hollow ZnFe2O4 nanospheres were successfully synthesized by a solvothermal precipitation method firstly; based on this, a C shell precursor phenolic resin was coated on the ZnFe2O4 hollow nanospheres' surface by an in situ oxidative polymerization method, and then ZnFe2O4@C was obtained by high-temperature calcination. Samples were characterized by SEM, TEM, XRD, XPS, BET, VSM, VNA. The results show that the maximum reflection loss (RLmax) reaches -50.97 dB at 8.0 GHz, and the effective bandwidth (EAB) of hollow core-shell structure ZnFe2O4@C is 3.2 GHz (6.16-9.36 GHz) with a coating thickness of 3.5 mm. This work provides a useful method for the design of lightweight and high-efficiency microwave absorbers.

Synthesis of palygorskite supported spherical ZnS nanocomposites with enhanced photocatalytic activity

The acquired nanocomposites exhibited a significant enhancement in photoactivity for the degradation of rhodamine B under simulated sunlight irradiation.