Abstract
Graphene oxide based nano-composites have attracted huge attention for wastewater treatment specially removal of heavy metals. This paper reports adsorption of onto modified magnetic graphene oxide with chitosan and cysteine (GO/ /Chi/Cys). To study the adsorbent morphology, Field Emission Scanning Electron Microscope (FE-SEM) and Fourier Transform Infrared Spectrometer (FTIR) were used in different stages of surface modification. In order to reveal the nature of sorption process, linear forms of different adsorption isotherms such as Langmuir, Freundlich, Tempkin, and Dubinin–Radushkevich were studied. Experimental data were fitted well by Langmuir model with a maximum monolayer coverage capacity ( ) of 86.21 . Prediction of from Langmuir model was in good agreement with maximum empirical adsorption capacity ( =85.4 ). Various types of kinetic models such as pseudo-first-order, pseudo-second-order, Elovich, and intra particle diffusion were investigated to determine characteristic parameters in the adsorption process. The kinetic studies showed that pseudo-second-order model represents the adsorption process better than others due to its high correlation coefficient ( =0.9996). Therefore, the adsorption process is chemisorption.
Highlights
Discharge of heavy metals into water as industrial wastes produced by battery producers, chemical products producers, metallurgy plants, paint producers, farmers, mines and the like has become one of the most serious environmental problems
The absorption bands at 1384 and 1121cm−1are both attributed to υ(C-O) mode. Another band is observed at 3411cm−1that can be assigned to the υ(OH) vibration. This absorption band is wider in the IR spectra of graphene oxide (GO)/Fe3O4 (Figure 2b), which may be due to υ(OH) groups from Fe3O4 particles
The band observed at 624cm−1is attributed to the vibration of Fe– O stretching, which confirms that Fe3O4 particles have been bonded to GO nanosheets
Summary
Discharge of heavy metals into water as industrial wastes produced by battery producers, chemical products producers (e.g. plastic, glass and ceramic), metallurgy plants, paint producers, farmers, mines and the like has become one of the most serious environmental problems. There are some drawbacks for most of these adsorbents including low adsorption capacity, agglomeration, oxidizing in contact with the atmosphere and producing secondary water pollution after adsorption process [13] To overcome these problems preparation of composite with other materials (surface modification) and using magnetic separation technique (MST) can be solutions. The excellent properties of GO such as high specific surface area and the presence of functional groups with oxygen (e.g. hydroxyl, epoxy, carboxyl, and carbonyl) in its structure have made it an effective material in the synthesis of different nanocomposites [16,17,18] These functional groups can play an important role in trapping metal cations. Investigation of different adsorption kinetics models provides useful information to understand the dynamics of adsorption process [26]
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