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Application of combined physical and chemical methods for the removal of textile pollutants from aqueous solutions

Author: Mocanu Larisa
Degree:doctor of chemistry
Speciality: 02.00.20 - Ecological chemistry
Scientific adviser: Gheorghe Duca
doctor habilitat, professor, Moldova State University
Scientific consultant: Maria Gonţa
doctor habilitat, professor, Moldova State University
Institution: Moldova State University


The thesis was presented on the 31 October, 2022
Approved by NCAA on the 25 November, 2022


Adobe PDF document1.13 Mb / in romanian


CZU 628.16.08.06:547.625(043)

Adobe PDF document 6.61 Mb / in romanian
211 pages


organic textile pollutants, dyes, auxiliaries, oxidizers, coagulants/flocculants, activated carbon, synthetic effluents, textile wastewater, physical and chemical methods, purification processes


The structure of the dissertation consists of introduction, six chapters, sevem general conclusions, four recommendations, a list of references (299 titles), six appendices. The content of the dissertation is reflected on 89 pages of the main text, supplemented by 30 tables, 45 figures, and three schemes. The results are published in 60 scientific articles.

The aim of the work – establishing the optimal conditions for the purification of synthetic effluents and wastewater from textile industries from dyes and excipients by using combined physical and chemical methods, developing schemes and introducing them into the treatment process, in order to maintain an admissible chemical content of natural waters, according to the standards.

Research objectives include selection of research and analysis methods, as well as their adaptation to oxidation/mineralization processes and the concentration of textile pollutants in industrial wastewater; establishing the optimal conditions for carrying out decontamination processes and evaluating the performance of removal of textile pollutants from industrial wastewater by applying advanced oxidation processes and concentration methods; proposing industrial wastewater treatment schemes containing textile pollutants by applying combined physico-chemical methods in order to reduce the negative impact of pollutants on the environment; extrapolation of the obtained results on synthetic effluents on textile industrial wastewater.

Scientific novelty and originality consist in the fact that, for the first time, the influence of auxiliary agents on the efficiency was established, by reducing the COD values up to the MAC (6.0÷8.0 mgO/L) by applying combined physico-chemical methods. Based on the results obtained, for the first time, it was found that the presence of auxiliary agents (LASS, Bis-MPA, DEG, EG) in the studied synthetic effluents that also contain colouring agents, increases the degree of oxidation/mineralization by 10.0÷25.0 %, due to the formation of intermediate compounds, which regenerate additional sources of ·OH.

The results obtained, contributing to the solution of an important scientific task consist in remedying inconveniences related to the protection of water bodies and increasing the quality of surface waters - the main task of ecological chemistry. For more efficient treatment of textile wastewater, the methods of concentration with POA and adsorption on activated carbon were combined. The quality of treated water allows both their discharge into natural receptors, without changing the chemical composition of natural waters, and their reuse in industrial processes, saving up to 60.0% of water consumption.

The theoretical significance consists in determining the influence of auxiliaries with hydrophilic and hydrophobic properties, the molecular mass and the association factor of the dyes on the treatment processes by applying combined physical-chemical methods. The presence of auxiliaries with strong hydrophobic properties (LASS, PO) and dyes (D) with less polar groups (RO, RR) leads to obtaining a high electroflotation efficiency. Based on the obtained results, the series of electroflotation efficiency was developed: LASS–D>PO–D>DEG–D>Bis-MPA–D. It was found that the presence of auxiliaries with strong hydrophilic properties (Bis-MPA, DEG and EG) and dyes with more polar groups (DR), increases the coagulation efficiency, because it increases the degree of association through the formation of hydrogen bonds between -OH groups of auxiliary agents and -NH2 functional groups of colouring agents.

The applicative value of the work consists in the extrapolation of the laws and optimal conditions obtained for the synthetic effluents waste treatment on the textile wastewater treatment. The development of schemes for their reuse in technological dyeing processes. The scientific results obtained on a laboratory scale guarantee a high treatment performance, about 90.0% for textile wastewater and up to 99.0% for synthetic effluents.

Implementation of scientific results. The scientific results obtained were appreciated by the Gheorghe Asachi Technical University, Iasi and were taken over by SA Apa-Canal Chisinau, in order to optimize the wastewater treatment processes. The results were used to elaborate lectures and laboratory works in the disciplines of Ecological Chemistry, Wastewater Treatment Technologies and the Economy of Sustainable Industrial Products, MSU, can be used to justify national/international projects within the strategic direction Materials, technologies and innovative products (ecological water chemistry field).