Biodegradability enhancement of waste lubricating oil regeneration wastewater using electrocoagulation pretreatment.

As a sustainable management of fossil fuel resources and ecological environment protection, recycling used lubricating oil has received widespread attention. However, large amounts of waste lubricating-oil regeneration wastewater (WLORW) are inevitably produced in the recycling process, and challenges are faced by traditional biological treatment of WLORW. Thus, this study investigated the effectiveness of electrocoagulation (EC) as pretreatment and its removal mechanism. The electrolysis parameters (current density, initial pH, and inter-electrode distance) were considered, and maximal 60.06% of oil removal was achieved at a current density of 15 mA/cm2, initial pH of 7, and an inter-electrode distance of 2 cm. The dispersed oil of WLORW was relatively easily removed, and most of the oil removal was contributed by emulsified oil within 5-10 µm. Gas chromatography-mass spectrometry (GC-MS) analysis revealed that effective removal of the biorefractory organic compounds could contribute to the improvement of biodegradability of WLORW. Thus, the 5-day biochemical oxygen demand/chemical oxygen demand ratio (BOD5/COD) was significantly enhanced by 4.31 times, which highly benefits future biological treatment. The routes of WLORW removal could be concluded as charge neutralization, adsorption bridging, sweep flocculation, and air flotation. The results demonstrate that EC has potential as an effective pretreatment technology for WLORW biological treatment.

[Preparation of porous polylactic-acid/ bone matrix gelatin composite as scaffold materials for bone-tissue engineering].

OBJECTIVE: To develop a novel porous poly lactic-acid(PLA)/bone matrix gelatin (BMG) bioactive composite biomaterial with supercritical carbon dioxide (SC-CO2) extraction and determine the optimal proportion of the ingredients by evaluating the physical and chemical characteristics and cellular compatibility of the composites. METHODS: The PLA/BMG composite biomaterials with various PLA/BMG proportions were prepared with SC-CO2 technique and evaluated by macroscopic observation, porosity and mechanical assessment, and scanning electron micrograph (SEM). The optimal proportion of PLA/BMG was determined in conjunction with the results of cellular compatibility evaluation. RESULTS: BMG proportion in BLA/BMG composite biomaterials prepared with SC-CO2 technique was positively associated with the cellular compatibility and porosity, and inversely with the mechanics of the prepared composite. The results showed BMG content of 30% in PLA/BMG composite was optimal. CONCLUSION: The composite with PLA and BMG proportion of 7:3 possesses good physical and chemical characteristics and cellular compatibility, suggesting its potential as the bone implant biomaterial and bone-tissue engineering scaffold.