Removal of Chromium from Leather Industry Waste Water by Activated Clinoptilolite


Abstract: Possible use of acid activated Balğkesir-Bigadiç clinoptilolite for the removal of chromium from leather industry wastewaters was investigated. HNO$_3$, H$_2$SO$_4$ and HCl were used for the activation of clinoptilolite and the effects of pH, acid concentration, particle size, solid/liquid ratio, time and temperature on activation were determined by chromium adsorption tests. Experimental results show that chromium can be adsorbed in the form of Cr$_2$O$_7^{2-}$ ions at pH=1.35 and the adsorption capacity of the clinoptilolite depending on the acid used for activation decreases in the order HNO$_3>$H$_2$SO$_4>$HCl. A series of tests considering Cr concentration, clinoptilolite/Cr solution ratio and time were carried out using samples activated with 2M HNO$_3$ and 3M H$_2$SO$_4$. It was observed that the chromium adsorption capacities of the clinoptilolites activated with HNO$_3$ and H$_2$SO$_4$ (Cr concentration=100 ppm, clinoptilolite/Cr solution ratio=1/2 mg/ml) for durations of 60 and 120 minutes were 0.061 mg/g and 0.064 mg/g respectively. Finally, adsorption tests were done with wastewater obtained the from U¤ur-Gül Leather Company containing 3120 ppm Cr under pre-determined optimum conditions and adsorption capacities for HNO$_3$ and H$_2$SO$_4$ activated clinoptilolite samples were determined as 0.624 mg/g and 0.201 mg/g respectively. Upon dilution of the chromium content of the wastewater to 100 ppm, these values decreased to 0.045 mg/g and 0.019 mg/g.

Keywords: Adsorption, Acid activation, Chromium, Clinoptilolite, Zeolite.

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