Blasting demolition has been widely used in the safe and efficient demolishing of construction buildings. Blasting demolition dust is the most visible and realistic harmful material during the blasting process. The characteristics and suppression of the blasting dust are scarcely addressed in the literature. This article investigated the micromorphology characteristic of blasting demolition dust from a typical building demolition project. The dust median size value D50 was 65.890 μm, and it showed a character of smooth edge, fluffy structure, and cracks. It consists of higher content of heavy metals than conventional cement powder particles, which include Mn, Ni, Zn, and As elements. The dust cannot be wet by municipal water for its hydrophobic character. A novelty method was proposed to set a methodology to form a stable, larger volume, and surface area water droplet on a rod stand, which provided more opportunities to find out and verify the microscopic agglomeration phenomenon and effectiveness between dust and different wetting droplets. The single dust-droplet collision results can be accurately recorded by the high-speed camera with a microscope, the collision and submergence time between blasting demolition dust particle and municipal water droplet on the stand was 2 ms, while the time was 1.125 ms with surfactant solution droplet, which was much shorter than the time of municipal water. The dust-droplet microscopic collision results were shown that the blasting demolition dust can be better wet and agglomerated by a surfactant solution. In blasting demolition projects, the BDD suppression methods with surfactant solution explosion mist have the highest efficiency, which can restrict the BDD’s concentration to 10 mg/m3.
The typical smelting wastewater is with characteristics of high concentration of TDS, conductivity, heavy metal ions, and low concentration of COD. The ultrafiltration (UF) and reverse osmosis (RO) is an attractive technology to reclaim and reuse this kind of wastewater. In this work, Coagulation-flocculation-sedimentation (CFS) and multi-media filter (MMF) was used as the pretreatment processes. UF, RO and concentration RO (CRO) processes was applied as the advanced treatment processes to reclaim the smelting wastewater. To enlarge the recovery of RO and CRO units, the influences of increasing the feed temperature by waste heat from the smelting plant and the feed pressure by change the operating frequency of the high pressure pumps were investigated. The optimize operation parameters of RO and CRO units were obtained. To understand the operation CIP cycle time of UF, RO and CRO membrane units in a long term operation, the trans-membrane pressure (TMP) and permeate flux difference were investigate. Good system operation stability, permeate flux recovery after CIP and qualified treated water were obtained in the recommend operation parameters. The results of this work can benefit to the designing of reclaiming the smelting wastewater by UF-RO-CRO approach within the Lead and Zinc smelting industrial application.
Modified activated carbon/carbon nanotubes (AC*/CNT*) composite electrode was used as the electrode in a capacitive deionization (CDI) process for desalination in this study. The morphology and electrochemical characteristics of the modified electrode were discussed, and the results showed that after modification, the specific surface area of AC* reached 672.48 m2/g, increased by 29.43%; while the specific surface area of CNT* was 117.39 m2/g, reduced by 9.94% due to the strong oxidation of the mixed acid, the pore volume of CNT* increased by 48.28%. The electrode regeneration test proved that the electrode had good cycling stability. The pseudo-first-order kinetic model could better describe the adsorption rate of the electrodes for ions and the desalination ratio of the AC*/CNT* electrode reached 7.11 mg/g; the Langmuir model could well describe the adsorption mechanism of capacitive deionization, and indicated that the adsorption process of CDI was near to single ion layer adsorption; the change trend of electric mobility with migration time could be well fitted by exponential equations. This study explored a novel composite electrode coating, and initially explored the behavioral characteristics and trends of CDI technology.
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