Applicative Study (Part I): The Excellent Conditions to Remove in Batch Direct Textile Dyes (Direct Red, Direct Blue and Direct Yellow) from Aqueous Solutions by Adsorption Processes on Low-Cost Chitosan Films under Different Conditions

Abstract

In recent years the development of chitosan (CH) based materials as useful adsorbent polymeric matrices is an expanding field in the area of adsorption science. Even though CH has been successfully used for dye removal from aqueous solutions due to its low cost, no considerations have been made about, for example, the effect of changing the pH of chitosan hydrogelor about the dehydrating effect of Ethanol (EtOH) treatment of chitosan film on the dyes removal from water. Consequently in our laboratory we carried out a study focusing the attention, mainly, on the potential use of CH films under different conditions, such as reducing the intrinsic pH, increasing the hydrophobic character by means of ethanol treatment and neutralization of CH films to improve their absorption power. Textile anionic dyes named Direct Red 83:1, Direct Yellow 86 and Direct V. Rizzi et al. 455Blue 78 have been studied with the aim of reducing the contact time of CH film in waste water improving the bleaching efficiency. Neutralized acid CH film and longtime dehydrated one result to be the better films in dye removal from water. Also the reduction of the CH solution acidity during the film preparation determines the decreasing of the contact time improving the results. The effect of initial dye concentration has been examined and the amount of dye adsorption in function of time t, qt (mg/cm 2 ), for each analyzed film has been evaluated comparing the long term effect with the decoloration rate. A linear form of pseudo-first-order Lagergren model has been used and described. The best condition for removing all examined dyes from various dye solutions appears to be the dehydration of a novel projected CH film obtained by means of the film immersion in EtOH for 4 days. Also CH films prepared by well-known literature procedure and neutralized with NaOH treatment appear having an excellent behavior, however the film treatment requires a large quantity of water and time.

An Alternative Use of Olive Pomace as a Wide-Ranging Bioremediation Strategy to Adsorb and Recover Disperse Orange and Disperse Red Industrial Dyes from Wastewater

“…If the obtained results are compared with similar studies, i.e., works related to the removal of disperse dyes reported in references [4][5][6]8,9,[12][13][14], the performance of the pomace appears, removing in a few minutes a very great amount of dyes. Additional values are also put forward, considering the desorption of dyes, proposing the recovery of both the adsorbent and dyes in a reasonable short time and with a simple method.…”

“…The following values, expressed in M −1 cm −1 units, were obtained: 7000 for DO (pH 3.5), 4400 for DR (pH 3.5) and 20,000 for dB 4000 (pH 6.0), and were used to infer the dye concentrations, at several contact times when in the presence of OP. In accordance with literature [13,15,24], the OP adsorption capacity q t (mg g −1 ) at time t for each dye, was calculated by applying the following equation:…”

“…Moreover, another important aspect to be considered is that, as suggested by Colorprint Fashion, the disperse dyes are industrially applied using a mixture of water and acetic acid. Therefore, the dye recovery process developed in this paper, making use of the same solvent (acetic acid), could be considered a virtuous more eco-sustainable cycle, in comparison with similar papers [4][5][6]8,9,[12][13][14].…”

Removal from wastewater and recycling of azo textile dyes by alginate-chitosan beads

“…Recently, it has been also demonstrated that the adsorption of dyes by means of natural and biodegradable polymers is one of the emerging methods for dye removal. Indeed, numerous studies based on the use of biopolymers, such as alginate [16,17] and chitosan [18][19][20], have established that these biosorbents have a very high affinity for many classes of dyes. Sodium alginate (AL), the sodium salt of alginic acid, is a linear biopolymer extracted from brown algae containing β(1→4)-D-mannuronic acid (M) and α(1→4)-L-guluronic acid (G) residues.…”

Operational parameters affecting the removal and recycling of direct blue industrial dye from wastewater using bleached oil mill waste as alternative adsorbent material

“…In this field the Authors of this paper have years of experience presenting innovative methods and materials with great performances in decoloring wastewater. [9][10][11][12] Overall, for these purposes, physical adsorption is presented as a simple method with several advantages: ease of operations, simplicity of design, high efficiency and low cost applications in water decoloration processes. Among adsorbent materials for wastewater treatment, the agricultural wastes are very interesting sorbent materials requiring little processing, but showing good adsorption capacity, selectivity, low cost, free availability and easy regeneration.…”