Introduction
The textile industry is the major source of water consumption and wastewater
pollution. These wastewaters generated from textile industries are linked to emerging
wastewater pollution problems. It contains a mixture of different dyes, auxiliaries,
additives, and additional chemicals that were added during textile production
processes, causing serious environmental concerns. However, the main problematic
pollutants from textile factories in the aquatic environment are dye mixtures.
The direct discharge of dyes in concentrations higher than 1.0 mg/L, treated or not,
could increase community complaints and concerns. This is primarily due to the
aesthetic problem linked to these dyes, especially for the non-acceptable colors of
river water such as red or purple compared to more accepted colors such as green or
blue. In addition, textile dyes in high concentrations inhibit sunlight penetration,
respiration activities and consequently inhibiting the biological and photosynthesis
processes in the aquatic environment.
Furthermore, the presence of these dyes for a long time in watercourses leads to dye
accumulation in fishes and other organisms. Some dyes decompose to corresponding
hazardous compounds that may also have a negative impact on the aquatic
environment. Moreover, azo compound dyes, which are widely used in textile
manufacturing and their related products (aromatic amine), can cause allergies,
dermatitis, skin irritation, carcinogenic and mutagenic modifications as well as acute
and chronic toxicity. Therefore, the treatment of these textile effluents is in demand.
The aim of the study is to evaluate the efficiency of removing simulated systems by
elctroflotation methods. The related objectives were to (i) determine the chemical
oxygen demand of mixtures that containing direct red dye and one or more types of
textile auxiliaries and (ii) comparing these results.
Materials and methods
In this research were used direct red dye 81 (50.0%), 2,2-
Bis(hydroxymethyl)propionic acid (98,0%), lignosulfonic acid sodium salt (average
Mw~52,000 and Mn~7,000), and diethylene glycol (99.0%).
A rectangular column has been used as electroflotation cell. Its length was 8.5 cm, its
width 8.7 cm and its height 17.5 cm. It was provided with two electrodes: carbon
anode and a stainless steel cathode. These two electrodes were supplied by a D.C.
power supply. The electrodes were placed on the bottom of the cell. COD

concentration was measured by potassium dichromate standard method using UV-Vis
spectrophotometer T 80+.
Results and conclusions
The electroflotation method is based on the principle of the electrochemical processes
of oxygen and hydrogen evolution during electrolysis of waste waters. Finely
dispersed gas bubbles raise the surface trapping along with them dispersed particles
present in solution. The foam layer obtained (floto sludge) is removed from the surface
of the solution by mechanical means.
In this study, electroflotation method is used for four simulated systems with variable
concentration auxiliaries (20,0-80,0 mg/L). Results are showed in Table 1.
Table 1. COD of simulated systems by electroflotation; [DR]0=200.0 mg/L,
J=0,5 Am-2, electroflotation time=10 min, Vwork solution=0.25 L

The emollient agent, Bis-MPA, has several hydrophilic groups than other auxiliary
agents and which, respectively, provide more water solubility. This agent has property
to prevent the electrofilter removal by the oxygen and hydrogen molecules generated
by water hydrolysis. Therefore, with increasing the emollient concentration in the
system, COD increases. But when a direct dye with negative charge is added to the
system, bis-MPA-DR, the hydrophilic groups (3HO groups) of the emollient interact
with the dye molecules, which in turn act as collectors in the electrofloatation system.
Thus, COD shrinks almost twice as much as the Bis-MPA system. In the case of the
third and fourth systems, the COD value is increased because with the addition of the
LASS and DEgl coupling, there is a change in the dimensions and the electrical charge
of the dye. As a result, CCO increases with increasing concentration of auxiliaries in
the systems studied, because electrolytic gas bubbles interact differently, and the dye
loses its collector property of organic matter in the foam layer. The electrofloating
process was followed by the activated charcoal adsorption process (KAY-1) for
systems whose COD values are greater than 6,9 mgO/L. Adsorption of residual
compounds takes place up to admissible rules (CMA). By comparison, the efficiency
of coating systems containing direct dyes is 14.0% higher than systems that have
active dyes in their composition. At concentrations higher than 200.0 mg/L of dye it
is necessary to apply destructive methods, in case of oxidation with Fenton reagent
after the electrofloating process.