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J. Environ. Treat. Tech.
J. Environ. Treat. Tech.
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Abstract: |
Hexavalent chromium Cr (VI) is a toxic material used in many industries such as tanneries and electroplating industries. Most of the
previous researches studied the removal of chromium at lower concentrations up to 600 mg/L but did not tackle the behavior at higher
concentrations, which resemble the real concentration of studied tanneries effluents. The present research is a comparative study of
different agricultural low cost adsorbents in the removal of high Chromium concentration from industrial wastewater up to 1000 mg/L,
compared to a commercial activated carbon. The tested adsorbents are (Banana Waste (BW), Sawdust (SD), Phragmites Australis (PA),
Sugarcane Bagasse (SCB), Pea pod peels (PPP) and Rice straw (RS)). The materials were chemically pretreated with acid-alkali except
BW was treated with acid only, to improve adsorbent metal binding capacity. Batch experiments were conducted to study the effect of
pH, adsorbent dosage, contact time, initial Chromium concentration and temperature on the removal efficiency of Chromium from
wastewater. The experiments were conducted in two sets, one for lower concentration (25-50-100-200-400) mg/L and the other for
higher concentration (600-800-1000) to simulate the concentration of Chromium in tannery industry effluents. At 1000 mg/L initial
concentration, BW achieved the optimum removal efficiency of 73.28% at pH = 3, adsorbent dosage = 25 g/L and contact time of 3
hours with the adsorption capacity was 39 mg/g. For SD at pH=2, 3 hours contact time, 10 g/L dosage, and 30oC the removal ratio was
64.83% and the adsorption capacity was 86.30 mg/g. The equilibrium data for various agricultural adsorbents was being tested with
various adsorption isotherm models such as Langmuir, Freundlich and Tempkin. At low concentrations, AC, BW, PA and SCB follows
Freundlich isotherm model while SD follows Langmuir isotherm model. At higher concentrations, BW, SD, PA follows Langmuir
isotherm while SCB follows Tempkin isotherm model. To evaluate the mechanism of Cr adsorption on different adsorbents, Pseudofirst-order and Pseudo-second-order equations were used. The adsorption process follows Pseudo-second-order for all adsorbents, which
confirms the chemisorption of Cr (VI) on different adsorbents.
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