Influence of inherent minerals on metalworking fluids sludge pyrolysis: Products characterization and heavy metals behavior.

Safely and appropriately disposing of metalworking fluids sludge (MFS) remains a challenge owing to its highly hazardous properties, this work investigated MFS pyrolysis at various temperatures (500, 600, 700, 800, and 900 °C) for energy recovery and safety treatment of MFS. The experimental results indicated that inherent minerals at higher temperatures could enhance the gas yields and promote the qualities of oil and gas from MFS pyrolysis. The highest pyrolysis gas yield was achieved at 18.86 wt% after MFS pyrolysis at 900 °C. GC-MS analysis revealed that the inherent minerals facilitated a decrease in oxygenated and nitrogenated compounds within the oil, while simultaneously leading to a substantial increase in hydrocarbon contents. Notably, the highest content of aromatics (61.16%) was attained during pyrolysis at 900 °C. Moreover, inherent minerals improved carbon sequestration and the characteristics of biochar during the MFS pyrolysis. The leaching contents of heavy metals in biochars were reduced, thereby reducing the heavy metals associated environmental risk. This research suggests that the pyrolysis process was a promising approach for simultaneous energy recovery and MFS disposal with low environmental risk.

Efficient removal of mercury ions with MoS2-nanosheet-decorated PVDF composite adsorption membrane.

The exploitation of a new adsorbent with a high adsorption performance and recyclability is of great practical significance for the treatment of wastewater containing mercury ions. In this study, a novel membrane adsorbent was fabricated by blending MoS2 nanosheets into a PVDF polymer matrix (P-PVDF/MoS2) followed by non-solvent-induced phase conversion. This material was able to bind mercury ions and was not affected by the solution ionic strength, co-existing anions, or interfering heavy metal ions. The optimal pH range for mercury ion elimination was 4.5-6.0, and P-PVDF/MoS2 exhibited a maximum adsorption capacity of 578 mg g-1. The pseudo-second-order adsorption kinetics and Langmuir isotherm models best described the adsorption process. The adsorption mechanism was mainly monolayer chemisorption, for which the S groups were the major active sites. Furthermore, the membrane could be removed from the aqueous solution easily using tweezers, and the removal efficiency of mercury ions remained over 90% after ten cycles. This study suggests that the inexpensive and recyclable P-PVDF/MoS2 membranes can be used for the efficient removal of heavy metal ions from wastewater at a large scale.

Amido-functionalized carboxymethyl chitosan/montmorillonite composite for highly efficient and cost-effective mercury removal from aqueous solution.

The efficient and cost-effective removal of mercury (Hg) from water is highly desired. A biopolymer/clay composite adsorbent was developed by introducing montmorillonite modified with sulfhydryl into a hyperbranched polyethylenimine functionalized carboxymethyl chitosan matrix (HPFC/MT-S), which proves to be a superior alternative for the removal of Hg(II) ions from aqueous solutions. The developed adsorbent exhibits excellent adsorption capacity of 1875 mg/g, representing the highest value among the reported polymer/clay composite adsorbents so far, and the concentration of Hg(II) ions was found to decrease from 1000 mg/L to 0.031 mg/L after adsorption by HPFC/28%MT-S, satisfying China's industrial wastewater emission standards. In addition, the selectivity of the composite for Hg(II) was further improved by the introduction of MT-S, yielding a high distribution coefficient value (Kd = 1.0 × 107). The adsorption capacity of HPFC/MT-S for Hg(II) is not equal to the simple sum of each component in the composite system but higher than that. The improved adsorption performance is mainly contributed to the increased porosities and chelation sites of the adsorbent. The present work suggests the great potential of polymer/clay composite materials in environmental remediation.

Determination of phthalate esters in airborne particulates by heterogeneous photo-Fenton catalyzed aromatic hydroxylation fluorimetry.

The environmental contaminants phthalic acid esters (PAEs) were determined by aromatic hydroxylation fluorimetry combined with heterogeneous photo-Fenton process in the presence of vermiculite supported BiFeO3 (VMT-BiFeO3). In strong alkaline solution, PAEs were hydrolyzed into phthalates with no fluorescence, which then reacted with hydroxyl free radicals produced in photo-Fenton process catalyzed by VMT-BiFeO3 to form the fluorescent hydroxyl phthalates. The fluorescence intensity was proportional to the concentration of PAEs with the maximum excitation and emission wavelength of 300nm and 417nm, respectively. A good linear relationship can be obtained in the range of 3.8×10-7 to 4.8×10-5molL-1 for DEP with correlation coefficient of 0.9997, and the sensitivity of the method was high with detection limit of 5.43×10-8molL-1. The method has been successfully applied to determine total PAEs in airborne particulates with satisfactory results.