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Removal of heavy metal Cu(II) in simulated aquaculture wastewater by modified palygorskite

Cao, Jia-Shun, Wang, Cheng, Fang, Fang, Lin, Jun-Xiong
Environmental pollution 2016 v.219 pp. 924-931
Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, adsorbents, adsorption, chelation, copper, cost effectiveness, electrostatic interactions, energy-dispersive X-ray analysis, heavy metals, models, pH, palygorskite, scanning electron microscopes, sorption isotherms, surface area, temperature, thermodynamics, thermogravimetry, transmission electron microscopy, wastewater aquaculture, wastewater treatment
Palygorskite (PAL) is a good heavy metal adsorbent due to its high surface area, low cost, and environmentally compatibility. But the natural PAL has limited its adsorption capacity and selectivity. In this study, a cost-effective and readily-generated absorbent, l-threonine-modified palygorskite (L-PAL), was used and its performance for Cu(II) removal in simulated aquaculture wastewater was evaluated. After preparation, L-PAL was characterized by using Fourier transform infrared spectroscopy, scanning electron microscope, energy dispersive X-ray spectroscopy, X-ray diffractometer, X-ray photoelectron spectroscopy, transmission electron microscopy and thermogravimetric analysis. The impacts of pH, adsorbent dosage, contact time, and initial Cu(II) concentration on the adsorption capacity of L-PAL were examined. The Cu(II) adsorption capacity on L-PAL was enhanced almost 10 times than that of raw PAL. The adsorption isotherms of Cu(II) fit the Langmuir isotherms, and the adsorption kinetics was dominated by the pseudo-second-order model. The thermodynamic parameters at four temperatures were calculated, which indicated that the adsorption was spontaneous and endothermic. The adsorption mechanism involves complexation, chelation, electrostatic attraction, and micro-precipitation. Furthermore, L-PAL is shown to have a high regeneration capacity. These results indicate that L-PAL is a cheap and promising absorbent for Cu(II) removal and hold potential to be used for aquaculture wastewater treatment.