Treatment of Water Contaminated with Reactive Black-5 Dye by Carbon Nanotubes

Abstract

Most of the dyes used today by the textile industry are of synthetic origin. These substances, many of which are highly toxic, are in many cases not adequately filtered during the processing stages, ending up in groundwater and water courses. The aim of this work was to optimize the adsorption process of carbon nanotubes to remove an azo-dye, called Reactive Black-5, from aqueous systems. Particular systems containing carbon nanotubes and dye solutions were analyzed. Furthermore, the reversibility of the process and the presence of possible degradation phenomena by the dye molecules were investigated. For this purpose, the influence of different parameters on the adsorption process, such as the nature of the carbon nanotubes (purified and nonpurified), initial concentration of the dye, stirring speed, and contact times, were studied. The solid and liquid phases after the tests were characterized by chemical-physical techniques such as thermogravimetric analysis (TG, DTA), UV spectrophotometry, BET (Brunauer, Emmett, Teller), and TOC (total organic carbon) analysis. The data obtained showed a high adsorbing capacity of carbon nanotubes in the removal of the Reactive Black-5 dye from aqueous systems. Furthermore, the efficiency of the adsorption process was observed to be influenced by the stirring speed of the samples and the contact time, while purified and nonpurified nanotubes provided substantially the same results.

Semi-Continuous Adsorption Processes with Multi-Walled Carbon Nanotubes for the Treatment of Water Contaminated by an Organic Textile Dye

“…The TOC variation, for permeate and mother liquor, was to assume a degradation of dye molecule inside MWCNT layer, where a chromophore group was adsorbed at least, as demonstrated by UV-VIS, while part of organic carbon (OC) could remain in the permeate passing through the MWCNT layer. It is possible to hypothesize that inorganic carbon is generated by the decomposition of the dye into carbonates, bicarbonates, and dissolved CO2, as discussed in previous works [78].…”

“…The multi-walled carbon nanotubes (MWCNTs) used in this experiment were the same ones synthesized and characterized as reported in previous articles [67,78]. Briefly, they were synthesized using the catalytic chemical vapor deposition technique (CCVD) and obtained with a purity of 95%.…”

“…They can generally be used as reinforcing fibers [61][62][63][64][65] and as a material capable of efficiently adsorbing different substances [66][67][68][69][70][71][72][73]. A particular application for which carbon nanotubes have shown promise is the removal of dyes in wastewater [74][75][76][77][78].…”

“…In our previous work, the removal of Reactive Black 5 (RB5) dye from aqueous solutions with carbon nanotubes in static systems was investigated by evaluating the influence of the nature of the carbon nanotubes, the initial concentrations of dye, the stirring speed, and the times on the adsorption process [78].…”

“…In this work, in particular, we wanted to continue the previous research [78] by studying the absorption of the Reactive Black 5 dye from aqueous solutions with carbon nanotubes in semicontinuous processes, in order to search for the optimal conditions for the purification of water contaminated.…”