Functional Tissues Based On Graphene Oxide:Preparation And Adsorption Properties

The evolution of society pushes the development of industry, but water pollution by different kinds of dyes and heavy metals from factories is proposing a crucial worldwide environmental emergency. Compared to other methods, adsorption strategy has its own unique advantages such as low cost, high efficiency and feasibility of operation. The key to the application of absorption strategy is to choose a proper adsorbent. Graphene oxide (GO), with abundant oxygen-containing functional groups and excellent chemical stability, attracts attention in the removal of cationic dyes and heavy metal ions. However, graphene oxide and other adsorption materials suffer from the common difficulty in the post-separation of adsorbent/water, which hinders their practical applications. In this thesis, functional tissues with higher absorbability and better recycle capability were fabricated by using a facile approach, i.e., commercial tissues modified by graphene oxide, and were applied to absorb cationic dyes and heavy metal ions. The main contents and results of this thesis are listed as follows:1. Graphene oxide was prepared from graphite by modified Hummers' method and then was attached on the tissues by immersion and drying. The morphology and structure of functional tissues were characterized and analyzed by scanning electron microscopy (SEM), thermal gravity analysis (TGA) and Raman spectrometer. Results show that the crosslinking of commercial tissues and graphene oxide through hydrogen bonding enables the functional tissues to be completely recycled from water after adsorption, which can avoid any secondary pollution.2. The adsorption ability of functional tissues for methylene blue and rhodamine B was analyzed by UV-Vis spectrophotometer. Batch tests were conducted to investigate the adsorption performance, e.g. the impacts of adsorption time, initial concentration of dyes and adsorbent dosage on the adsorption performance. Results suggest that the adsorbance of functional tissues for the two dyes is strongly dependent on adsorption time, initial concentration and adsorbent dosage. Giving the initial concentration of methylene blue and rhodamine B of 40mg/L and 30mg/L, respectively, and the adsorption time of 2000min, the adsorption capacity is 54.84mg/g and 21.74mg/g, respectively. Moreover, functional tissues well solve the problem of adsorbent/water separation. It is noteworthy that graphene oxide sheets play a critical role in adsorbing the dyes. The adsorption capacity of functional tissues based on graphene oxide for rhodamine B is completely contributed by graphene oxide component. By calculating the graphene oxide loading in the tissue, the adsorption capacity for rhodamine B reaches 182.57mg/g at initial concentration of 30mg/L. Kinetic analysis reveals that the adsorption process for methylene blue and rhodamine B is well-matched with the pseudo-second-order kinetic model, indicating the dominance of chemical adsorption during the entire process.3. The adsorption performance of functional tissues for Pb(?) ions was evaluated by atomic absorption spectroscopy. Parameters including initial concentration of Pb(?) ions and adsorbent dose were investigated in detail. Results show that when initial concentration of Pb(?) ions is 200mg/L, the adsorption capacity of functional tissues reaches 28.34mg/g. Particularly again, all the adsorption capacity of functional tissues for Pb(II) ions comes from graphene oxide. Known the graphene oxide loading in the tissue, the adsorption capacity for Pb(II) ions is calculated as 487.51mg/g in the concentration range investigated in this study. Meanwhile, the adsorbance of functional tissues for Pb(II) ions increases with initial concentration and adsorbent dosage. Pseudo-first-order and pseudo-second-order kinetic models are applied to model the adsorption dynamics and the latter is found more proper to describe adsorption process. The Langmuir adsorption isotherm is applicable to describe the equilibrium adsorption process, indicating that Pb(II) ions adsorbed on functional tissues forms a monolayer structure.