Abstract
Fish scales (FS), a byproduct of the fish processing industry, are often discarded carelessly. In this present study, FS were used as a promising bio-sorbent for the removal of anionic acid dyes (acid red 1 (AR1), acid blue 45 (AB45) and acid yellow 127 (AY127)) from the wastewaters of textile coloration. Here, physiochemical characterizations of the FS were investigated by SEM-EDS, TGA and FI-IR analyses, and dye absorption and removal efficiency were evaluated and optimized considering different process parameters such as concentration of initial dye solution, amount of FS used, contact time, FS size, process temperature, additives, stirring and vacuum. SEM images and EDS elemental analyses showed architectural variation and heterogeneous composition of FS at different places. TGA identified the 50% minerals, 33% organic matters and 17% moisture and volatile components. FI-IR evidenced considerable absorption of acid dyes. Process optimization revealed that additives and fine pulverized FS had significant positive and negative impact on the dye removal efficacy, respectively. Temperature and stirring improved dye removal efficiency, and dye absorption by FS was very fast at the beginning and became almost constant after an hour indicating saturation of absorption. The maximum dye absorptions in scales for AR1, AB45, and AY127 were noted as 1.8, 2.7 and 3.4 mg/g, respectively, and removal percentages were 63.5%, 89.3% and 93%. The effects of the process parameters were consistent across all three acid dyes used in this study. Two-way ANOVA model showed that dye type, process parameters and ‘dye type X process parameters’ interactions had significant effect on the dye removal efficiency.
Highlights
Over two thirds of our planet is covered by water; only three percent is freshwater
The top side (Figure 1A) containing hard mineral has different orientations identified by numbers 1, 2, 3, 4 and 5: (1) The anterior field, the front part, separated by white inflexion lines called radii, has stair like ridges, (2) the focus, the center of the fish scales (FS), is relatively hard in structure with mosaic patterns, (3) the posterior field embedded to the body of fish is decorated with meander lined tiles, (4) the circuli covering maximum area of the scale is featured with arc type lines, and (5) the lateral field that distinguishes the circuli and the posterior field [26]
The viability of FS for the removal of acid dyes by absorption process was investigated by physiochemical characterization (SEM-Energy dispersive X-ray spectroscopy (EDS), TGA and Fourier transform infrared (FT-IR))
Summary
Over two thirds of our planet is covered by water; only three percent is freshwater. Out of this tiny amount, less than one third is potable, since the remaining portion is locked in the form of glaciers, ice, and snow on the north and south poles [1]. Two-thirds of the freshwater is withdrawn for industrial purposes such as chemical, agriculture, leather, cosmetic, steel, refinery, cement, and textile processing. In addition to consuming a significant portion of available freshwater, the textile industry has come under scrutiny for polluting water with its waste [2]. The wastewaters of textile coloration contain nonbiodegradable synthetic dyes, high oxygen demanding materials, and other noxious chemicals [3]. As a result, when these wastewaters are discharged to the environment without any treatment, it adversely affects all the basic biotic and abiotic components of environment including the hydrosphere, lithosphere and atmosphere [4]
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