Pyrolysis of low-density polyethylene using synthetic catalysts produced from fly ash

Catalytic pyrolysis of low-density polyethylene (LDPE) was investigated using various fly ash-derived silica–alumina catalysts (FSAs). FSAs were prepared by a simple activation method that basically includes NaOH treatment of fly ash by a fusion method, followed by an aging process. A series of LDPE pyrolysis experiments was conducted and the catalytic performance of FSAs was assessed in terms of the degradation temperature and the simulated boiling point distribution of the liquid products. The effects of synthesis conditions such as NaOH/fly ash weight ratio and aging time were examined by X-ray diffractometer (XRD), Brunauer-Emmett-Teller (BET) surface area analyzer, and scanning electron microscope to clarify the controlling factors affecting the catalytic activity. To obtain catalyst with high activity, it is necessary to produce sufficient silica and alumina species that can be easily co-precipitated into solid acid catalyst by destruction of the fly ash structure and to optimize the activation time for catalyst synthesis to prevent the transformation into inactive phases. The catalytic performance of FSA obtained from optimal conditions was equivalent to that of commercial catalysts, demonstrating the effectiveness of the catalyst.     

Wash water in waterworks: contaminants and process options for reclamation

Reclamation of clean water from filter backwash water was studied through pilot-scale experiments.The pilot plant consisted of clarification,sand-filtration,and ultrafiltration modules in sequence,with a provision to bypass the sand filter.Clean water that conformed to World Health Organization (WHO) guidelines on Potable Quality was reclaimed.Turbidity,aluminum and iron were found to be critical contaminants in process selection and design.Clarification,followed by sand filtration,was found to be the minim...     

Influence of physico-chemical properties of soil clay fractions on the retention of dissolved organic carbon

This study investigated the effects of surface functional groups, cation exchange capacity (CEC), surface charge, sesquioxides and specific surface area (SSA) of three soil clay fractions (SCFs) (kaolinite–illite, smectite and allophane) on the retention of dissolved organic carbon (DOC) in soils. Physico-chemical properties of the SCFs before and after removing native carbon and/or sesquioxides were characterised, and the DOC adsorption–desorption tests were conducted by a batch method. Native organic carbon (OC)/sesquioxide removal treatments led to a small change in the CEC values of kaolinite–illite, but significant changes in those of smectite and allophane. The net negative surface charge increased in all samples with an increase in pH indicating their variable charge characteristics. The removal of native OC resulted in a slight increase in the net positive charge on soil clay surfaces, while sesquioxide removal increased the negative charge. Changes in the functional groups on the SCF surfaces contributed to the changes in CEC and zeta potential values. There was a strong relationship (R ² = 0.93, p < 0.05) between the Langmuir maximum DOC adsorption capacity (Q _max) and SSA. The Q _max value also showed a moderately strong relationship (R ² = 0.55, p < 0.05) with zeta potential (at pH 7). Q _max was only poorly correlated with CEC and native OC content. Therefore, along with SSA, the surface charge and functional groups of SCFs played the key role in determining the adsorption affinity and hence retention of DOC in soils.     

Evaluating the effects of granular and membrane filtrations on chlorine demand in drinking water

In this study, chlorine decay experiments were conducted for the raw water from Nakdong river that is treated by Chilseo Water Treatment Plant (CWTP) situated in Haman, Korea as well as the effluents from sand and granular activated carbon (GAC) filters of CWTP and fitted using a chlorine decay model. The model estimated the fast and slow reacting nitrogenous as well as organic/inorganic compounds that were present in the water. It was found that the chlorine demand due to fast and slow reacting (FRA and SRA) organic/inorganic substances was not reduced significantly by sand as well as GAC filters. However, the treated effluents from those filters contained FRA and SRA that are less reactive and had small reaction rate constants. For the effluents from microfiltration, ultrafiltration, and nanofiltration the chlorine demand due to FRA and SRA were further reduced but the reaction rate constants were larger compared to those of sand and GAC filter effluents. This has implications in the formation of disinfection by products (DBPs). If DBPs are assumed to form due to the interactions between chlorine and SRA, then it is possible that the DBP formation potential in the effluents from membrane filtrations could be higher than that in the effluents from granular media filters.     

A comparison study of the potential risks induced in arable land and forest soils by carcass-derived pollutants

Environmental Geochemistry and Health - Improper decisions concerning animal carcass disposal sites pose grave threats to environmental biosecurity. However, only a few studies have focused on the...     

Comparison of endotoxin levels and gram-negative bacteria under different conditions in microbial laboratories and a biowaste site

In this study, we assessed airborne endotoxin levels in university laboratories, hospital diagnostic laboratories, and a biowaste site. We also investigated indoor and outdoor sampling, sampling site, type of ventilation system, presence of open biowaste boxes, weather, and detection of Gram-negative bacteria (GNB). A total of 69 air samples were collected from 11 facilities in three institutions. Average total airborne endotoxin levels ranged from <0.01 to 10.02 EU m⁻³, with an overall mean of 1.03 EU m⁻³. Endotoxin levels were high in window-ventilated facilities, in facilities in which GNB were detected; levels were also high when it was rainy (all ps < 0.05). Endotoxin levels were significantly correlated with humidity (r = 0.70, p < 0.01). The presence of HVAC; humidity; and the presence of open biowaste boxes affect endotoxin levels in laboratories.