Process simulation of bis (2- Hydroxyethyl) terephthalate and its recovery using two-stage evaporation systems

To preserve the petroleum feedstock and eliminate the environmental problems peculiar to polyethene terephthalate (PET) bottles littering the environment. Chemical recycling method was adopted to convert PET into useful products of prosperous sizeable industrial application. This work employed ASPEN PLUS V8.8 to simulate chemical glycolysis depolymerisation process of PET plastic wastes, using plug flow reactor for commercial production of pure bis (2- hydroxyethyl) terephthalate (BHET). The data for modelling were gotten from the experimental PET glycolysis depolymerisation work. Excess ethylene glycol (EG) was used to degrade PET waste with zinc acetate (Zn(Ac)2) as the active catalyst. The optimum operating conditions of the reaction were mean particle size PET of 127.5 μm, EG:PET (w/w) ratio of 5:1,469 K temperature, 101325 N/m 2 pressure and 3 h residence time. Reaction results were 100 % depolymerisation of PET, 85.24 % yield of BHET and 14.76 % Oligomer. Purification of the BHET was done with two stages evaporation processes using flash columns and crystallizer. Higher temperature and lower pressure were observed to increase the efficiency of the evaporators, but the heat duties increased and momentarily reduced the BHET recovery. BHET recovery was observed to decrease with increase in temperature in the case of crystallisation operation. This work achieved a higher yield and purity of BHET, a higher EG removal for re-use and less heat duties demanded in comparison to previous works. The processes with its operating conditions can be used for future scaling up of commercial processes

Quantification of environmental impacts of domestic wastewater treatment using life cycle assessment: A review

Life cycle assessment (LCA) is an analytical tool used to quantify the overall environmental impacts associated with products, processes or human activities from cradle to grave. The LCA is important to determine the impact of wastewater treatment and the technologies used on human health and the environment. It performs well to find the best solutions to improve the sustainability. Therefore, it is important to review how previous studies on wastewater treatment have applied LCA. This paper presents a wide-ranging review of papers published from 1990 to 2016 that have used a range of LCA to cover the objectives, boundaries, functional units (FUs) and life cycle impact assessment(LCIA) of wastewater treatment. The analysis of the reviewed papers revealed that there are some differences in term of the FUs, system boundaries, and LCIA methods. These differences normally contribute to obtaining a few non-prosaic results. Moreover, the FUs adopted in some reviewed studies were not able to achieve the purpose of providing a reference to ensure compatibility of the results. Therefore, it is highly recommended that more attention is paid to choosing the FU in future studies. Thus, to ensure the quality and comparability of LCAs, it is very important to develop the LCA guidelines and standards and the LCIA impact categories

Current developments in chemical recycling of post-consumer polyethylene terephthalate wastes for new materials production: a review

This paper appraised divergent chemical depolymerization routes for reprocessing chemically synthesis polyethylene terephthalate (PET) plastics bottle waste and offer resolutions to control the environmental complications emanating attributable to its utilize and disposal to the habitat. The consciousness to prune environs contaminants and make it “green” demand for the reclaim and reprocessing it back to PET bottles, precursor products like glycolyzate, and other inventions such as unsaturated polyester resins, epoxy resins, composites etc. Controlling this necessitates assorted reprocessing methods of which chemical recycling that transform PET into monomer/oligomer is the most prosperous one. This review explored in detail current events in the PET chemical recycling using glycolysis method. The study was based on their current evolution concerning their depolymerization agents, reaction conditions, kinetics of reactions, catalysts used, products of reprocessing, and their prospective use. Benefits of PET recycling and glycolysis as well as criteria and necessitation factors that used to adjudge them as the best method and sub-method respectively were highlighted. The prospect for the conversion of glycolyzate into other PET recycling methods products were shown. PET recycling was concluded to be a partial resolution to wastes management, and also grants the conservation of natural petrochemical resources and energy

Characteristics of the effluent wastewater in sewage treatment plants of Malaysian Urban Areas

Recently, a lot ofdomestic wastewater is being generateddue to therise in the population in most urban areas in Malaysia. Thisimplies that more contaminations are being producedwhich are likely to affect human health. The purpose of this research was to analyzethe level of contaminants in the final treated wastewater from the sewage treatment plants in Malaysian urban areas and compare it with Malaysian standard A and B effluent discharged. The specimens used for the analysis were obtainedfrom three wastewatersewage treatment plants in Johor (A), Kuala Lumpur (B), and Penang(C). Specimens were examined usingchemical oxygen demand (COD) Vials, Nitrate Nitrogen ammonia vial, and total Phosphorus vial. The Hach DR 5000 UV-V Laboratory Spectrophotometer was used to measure the amount of COD, Nitrate, Nitrate, and Phosphorus. Also, the pH, turbidity, and BOD5 were done utilizingdissolved Oxygen machine and Lovibond Turbidity Meters. The level of BOD, COD weretreated well and discharged according to the used standards. The findings revealed that phosphorus in plant c with 12 mg/Lin February, Nitrate in plant A 22 mg/Lin January, Nitrite in plant A with 18.2 mg/Lin February, 19.4 mg/Lin February in plant B and16 mg/Lin February were found little greater than the prescribed effluent standard of Malaysian wastewater.It was recommendedthat the final treated water should be frequently and thoroughly treatedfor the purpose of reusingit for secondary intent. This study has importantimplications forprotecting human health and the environment by identifying the effluent sewer treatment plant that has no proper treatment capability to produce water that is fit for domestic and irrigation purpose