When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.
Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.
Commonly used pharmaceutical products present in sewage cannot be removed by conventional wastewater treatment plants. Therefore, they can be found in effluents discharged to aquatic systems. Endocrine disrupting compounds (EDCs) are among these releases to environment. For example, 17α-Ethynylestradiol (EE2) is a synthetic compound extensively used by population, which releases into an environment. Thus, it can cause a negative effect on the endocrine system of aquatic biota and human.
To protect the aquatic system against an impact of EDCs comprised in the effluent, a novel system for their removal was proposed. A steroidal estrogen, EE2, was assumed to be a target compound in this investigation. Then, the objective of this study is to develop a sustainable system for EE2 removal. The methodological approach combining an adsorption with electro-kinetic phenomena has been proposed. Sustainability supposed to be based on revalorization of wasted materials and minimizing of energy use. Four phases of investigation were proposed, namely, phase 1: Manufacturing procedures; phase 2: Experimental protocol; phase 3: Suspended particles removal; phase 4: Simulation. The study has been advanced, where waste generated by fishery and forestry demonstrated already excellent material to build an electro-adsorptive system. Application of a low direct current (DC) also demonstrated a sufficient effectiveness of the system. In focus, to understand the partitioning of EDCs (EE2) between liquid and solid phases, in very beginning of this study, eight types of adsorbents made from New Adsorptive Materials (NAM) were using to remove EE2 from an aqueous solution. Afterward, these adsorbents were enhanced with New Adsorptive Materials (ENAM) to increase EE2 removal from an aqueous solution.
The analytical test showed that adsorption phenomena using these types of adsorbents adequately reduces EE2 in the aquatic solution. The obtained results of the analytical test were initially sorted based on the adsorbent type: 1. Adsorbent made from New Adsorptive Material called NAM (formed from softwood) showed 42% removal of EE2; 2. Adsorbent made from New Adsorptive Material called NAM (formed from hardwood) showed 47% removal of EE2.
As a competitive removal capacity with cost- effectiveness increase, it was proposed to enhance the best adsorbent which was shown by the primary results using chitin. This method (adsorbent enhancement method) showed 92% removal of EE2 which is prefect compared to NAM, but it is still far away from the research objective. Therefore, it was proposed to establish an electrical system able to support an adsorption phenomena. A combination technique was the choice. This technique was establish by a combination between a direct current (DC) method and adsorption phenomena (Electro-Adsorptive System). It was developed from these parameters: 1. Electrode materials replacement using Iron, aluminum, and carbon; 2. Voltage change using 5, 10, 15, 20, 30V; 3. Time of applied electrical field from 9h to 24h; 4. Adsorbent type change using different types of synthetic adsorbents. In the end of this work, an experimental comparison was made between synthetic adsorbents and commercial adsorbents.
The obtained results from the analytical test of EE2 removal were as follows: 1. 91% removal of EE2 using the absorbent made under these condition (H1T1); 2. 99.99% removal of EE2 using the adsorbent made of chitin; 3. 79% removal of EE2 using the commercial activated carbon adsorbent (CACA) made from Coconut shell; 4. 99.99% removal of EE2 using the enhanced adsorbent made from H1T1+chitin.
The preliminary study has already shown the possibility of EE2 removal by 99.99%. It is expected, that the developed system would be applied as an additional operation unit to polish effluents before discharge them into aquatic systems.