Abstract
In this study, the capacity of biochars, derived from the pyrolysis of tannery fleshing waste (TFW) at 400 °C; 500 °C and 600 °C, in removal of red dye Sella Fast Red (SFR) from aqueous solutions and tannery wastewater was investigated under various experimental conditions in batch mode. Results show that for all applied biochars, the removed kinetics data were well fitted by the pseudo-second-order model, and the equilibrium state was obtained after 240 min of contact time. For an aqueous pH of 6 and a red dye concentration of 75 mg·L -1 , the removed amounts increased from 26 mg·g -1 to 39.86 mg·g -1 when the used pyrolysis temperature was increased from 400 °C to 600 °C. Moreover, SFR adsorption data at equilibrium were well fitted by Langmuir model suggesting a probable monolayer adsorption process with a maximal removal capacity of 62.7 mg·g -1 for BTFW-600 °C. The thermodynamic study demonstrated that SFR adsorption was endothermic for the three tested biochars. Desorption experiments with distilled water proved that SFR was significantly desorbed from the tested biochars, which offers possible reusability. On the other hand, BTFW-600 °C has demonstrated an important ability in removing SFR from real wastewater since only one dosage of 15 g·L -1 was enough to ensure more than 97% of dye removal. According to pH ZC and FTIR analysis, the possible mechanism toward SFR dye removal was attributed to electrostatic interactions that occurred between biochar and functional groups of SFR. This work could provide guidance for the value-added utilization of tannery solid waste and a practical way to remove dyes from tannery wastewater.
Highlights
Leather industry plays a prominent role in the world’s economy, with an estimated global trade value of approximately US$100 billion per year [1]
The novelty of the present study is to investigate the removal of industrial dyes used for leather tanning using biochar produced by the waste generated by the same tannery
The pyrolysis of the tannery fleshing waste (TFW) demonstrated that the biochar yields were dependent on the used temperature (Table 1)
Summary
Leather industry plays a prominent role in the world’s economy, with an estimated global trade value of approximately US$100 billion per year [1]. During the leather process a large amount of solid wastes are generated such as hides and skins, fats, shavings and trimmings, buffing dust, process effluents, and sludge [3]. The most common way to manage solid wastes is by disposing of them on landfill sites [4]. Fleshing wastes are considered as major solid wastes (around 60%) generated from tannery and finite leather production [5]. Fleshings obtained from hides treated with a high percentage of sodium sulfide are found to be unfit for the production of glue. They are at best disposed through landfill. Disposal of such fleshings is currently a serious problem and new ways for the disposal of tannery fleshing waste (TFW) need to be found
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