Abstract
Layered double hydroxides (LDHs), also called anionic clays, consist of cationic brucite-like layers and exchangeable interlayer anions. These hydrotalcite-like compounds, with Zn and Al in the layers and chloride in the interlayer space, were prepared following the coprecipitation method at constant pH. The affinity of this material for Remazol Blue 19, RB19 [2-(3-(4-Amino-9,10-dihydro-3-sulpho-9,10-dioxoanthracen-4-yl) aminobenzenesulphonyl) vinyl) disodiumsulphate], was studied as a function of contact time, pH of the solutions LDH dose and the RB19/[Zn–Al–Cl] mass ratio. It was found that 48 h is enough time for the equilibrium state to be reached with maximum RB19 retention at pH of 9 for an LDH dose equal to 100 mg and with an RB19/[Zn–Al–Cl] mass ratio higher than 3. The adsorption isotherm, described by the Langmuir model, is of L-type. The results demonstrate that RB19 retention on LDHs occurs by adsorption on external surface when RB19/[Zn–Al–Cl] mass ratio is equal or <3 and by both adsorption and interlayer ion exchange for ratios higher than 3. A mechanism for removal of RB19 anion has been confirmed by X-ray diffraction, IR spectroscopy and TG analysis (TG and DTG curves).
Highlights
Industrial effluents from textile, tanneries or printing are polluting discharges that contain nonbiodegradable dyes (EL Gaini et al 2008a)
It was found that 48 h is enough time for the equilibrium state to be reached with maximum RB19 retention at pH of 9 for an layered double hydroxides (LDHs) dose equal to 100 mg and with an RB19/[Zn–Al–Cl] mass ratio higher than 3
Preliminary adsorption experiments were conducted to determine the optimal conditions for the retention of RB19 on LDHs regarding the pH value, contact time, initial concentration (Ci) of adsorbate and the mass ratio adsorbate /adsorbent
Summary
Industrial effluents from textile, tanneries or printing are polluting discharges that contain nonbiodegradable dyes (EL Gaini et al 2008a). Their decontamination by conventional techniques seems ineffective in some cases. The removal of colouring agents from textile effluents has attracted attention in the last few years, because of their toxicity, and mainly due to their visibility. In the field of textile, special attention was paid to these industries by developing research to identify costeffective methods of treatment of their releases coloured and meet required standards. Improper disposal of dye-containing wastewaters that cause aesthetic problems concerns the scientists, but is beginning to draw the public authority’s attention and can generate toxic effects to aquatic life. Effluents from textile dyeing are constituted by complex mixtures of dyes, auxiliary chemicals, salts, acids, bases, organochlorines and sometimes heavy metals (Goncalves et al 2000)
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