Direct and Reactive Dyes Recovery in Textile Wastewater Using Calcinated Hydrotalcite

Abstract

Growing environmental conservation concerns have led researchers to seek the means to treat and recover wastewater. The textile industry dumps vast quantities of wastewater from textile dyes. By means of clays, dye waste can be separated and reused for other industrial processes. Clay absorption varies depending on the type of dye employed because factors like the reactivity of the dye molecule and its size are very important during the absorption process. The absorption capacity of calcined hydrotalcite at several concentrations was compared in a 0.05 g • L-1 solution of four distinct dyes: Direct Blue 199, Direct Red 23, Direct Blue 71 and Reactive Yellow. Dyes have different molecular weights because the weight of reactive dyes is considerably lighter than that of direct dyes, which is why the Lambert-Beer lines of each dye are previously considered. We worked with a 5 g • L-1 clay concentration to introduce the dye into the clay by stirring for 24 h in 100 ml of each dye solution before filtering it and leaving it to dry. In all cases, the dye absorption by nanoclay was nearly absolute and the initial solution was very clean, which are excellent results from the wastewater treatment point of view. Color measurement was performed by a Jasco V-670, double-beam spectrophotometre between 190-2700 nm. Differences in color were calculated and represented in CIE-Lab* color space diagrams. Finally, thermogravimetric (TGA) and X-ray diffraction (XRD) analyses were carried out to ensure both nanoclay-dye interactions and hydrotalcite structure recovery. No large differences were observed under these conditions, which reinforces the idea of using low nanoclay concentrations.

Dyeing with Hydrotalcite Hybrid Nanoclays and Disperse, Basic and Direct Dyes

“…After a dyeing process by depletion, the dye remains in the dye bath; just as after the adsorption effect, the dye that has not been adsorbed may remain [47,70]. In order to determine the amount of dye in the form of g•L −1 concentration in each of these cases, simple regression models by Lambert-Beer [71] are used beforehand.…”

Complete Desorption of Hybrid Nanoclays Composed of Hydrotalcite and Disperse Dye

“…Adsorption studies were carried out with real dye wastewater, and the effectiveness of the adsorption method was proven. However, certain conditions were simulated in the laboratory, which are detailed below [ 63 , 64 ]. Five litres of dye bath were prepared with only the dye, without adding any type of salt, dispersant, or any other product, since the initial objective was to load the clay with only the dye.…”

The Optimal Concentration of Nanoclay Hydrotalcite for Recovery of Reactive and Direct Textile Colorants

“…Each sample solution of hybrid nanoclay-dye was stirred for 24 h, the first two hours at 1600 rpm and the remainding time at 600 rpm [ 72 ]. The next step was to filter the solution by gravity for 48 h through filter paper and measure with the spectrophotometer to calculate the concentration of dye that was not absorbed by the nanoclay [ 73 , 74 ]. The nanoclays with the dye were lyophilized [ 75 , 76 ] to completely extract the water.…”