The Use of Allochthonous Tropical Peat Swamps of Antananarivo for Dyes Elimination in Effluents

Abstract

Textile industries play an important role in the economy of developing countries. However, these industries are among the major consumers of water and chemical inputs. They reject considerable quantities of wastewater, the quality of which sometimes threatens the environment due to the inefficiency of the treatment methods used. This is combined with the inaccessibility to the advanced purification technologies because of their high cost. Many low-cost materials have been studied by scientists to treat effluents.  The ATP (allochthonous tropical peat) of Antananarivo, Madagascar, has aroused interest in the treatment of wastewater, especially for colored textile effluents. The physico-chemical characteristics of the ATP are determined, then the BLM dye (methylene blue) is used as a model dye for adsorption. After that, treatment tests in the form of filtration are carried out with textile effluent. This study showed that ATP removes cationic dyes more favorably than anionic ones at pH greater than 4.2, the zero-charge point of peat. The adsorption of BLM, a cationic dye, on ATP is physisorption and endothermic. A maximum of 20mg of BLM dye is adsorbed per gram of ATP and its follows the Langmuir model. The analysis of the IR spectra showed that the carboxylic function and the phenol group of the peat are involved on the dye fixation. The treatment of effluent taken from the textile industry revealed that ATP improves the pH and the color of the effluent; however, it increases the COD due to the presence of certain organic acids.