Research On The Preparation Of Graphene-Polymer Composites And Their Adsorption Behaviors Of Ciprofloxacin In Aqueous Solutions

Antibiotics remain in water are a class of refractory organic pollutants. They could enriched in the environment by bioaccumulation or biomagnification, which in turn promotes the production of resistant bacteria, potentially causing great potential threaten for the ecological environment and human health. Based on the characteristics of antibiotic such as ciprofloxacin in water, this paper encapsulated graphene oxide (GO) into environment-friendly natural polymer materials—sodium alginate (SA), obtained GO-SA-H and GO-SA-A. G-SA-DN composite gel was acquired through hydrothermal treatment. The influence of reaction time, antibiotics concentration, ionic strength, pH value and heavy metal on the adsorption capacities of adsorbents was studied to explore the development regularity of adsorption process and optimum adsorption conditions. The adsorption mechanism was also analyzed by adsorption kinetics and isotherm models.First, GO-SA-H and GO-SA-A were prepared by encapsulating GO into SA using calcium chloride hardening method. The result of characterization showed that GO could be well mixed with SA and specific surface area approximately increased 1.4 times. The pore size and distribution uniformity have a certain degree of optimization. Thermal stability also has been improved. The results of adsorption kinetics showed that adsorption capacities of SA hydrogel and aerogel were increased about 10 times after the encapsulation of GO,reached 25.37 mg/g. The kinetic adsorption data were fitting well with pseudo-second model,which indicates that the adsorption process is chemical adsorption. The adsorption isotherm experimental data are mainly in accordance with the Langmuir model. High concentration of ionic strength and high pH value can cause great damage to the adsorbent structure, and then the ball structure was disintegrated. Low concentration of Cu2+ can promote the adsorption performance of ciprofloxacin onto SA and GO-SA hydrogel and aerogel in aqueous solutions.Three-dimensional G-SA-DN composite gel was prepared by using environmentally friendly reducing agent ascorbic acid to reduce graphene oxide turn into graphene. After hydrothermal treatment, G-SA-DN gel appeared sponge-like structure, and the pore size was more concentrated in the range of 1-5 nm. In the reduction process of GO, G-SA-DN gel formed a double network structure, which improves the thermal stability at a certain degree.The experimental results showed that the adsorption capacity of G-SA-DN gel can reach to 71.71 mg/g, which is about three times higher than the previous material. The adsorption capacity of ciprofloxacin using Langmuir model can reachto 204.6 mg/g. The effects of ionic strength and pH on the adsorption of antibiotics by thermal treated SA and G-SA-DN gel were similar with earlier materials. And the material structure was completely destroyed. Low concentration of heavy metals can promote the adsorption capacities of ciprofloxacin onto SA and G-SA-DN gel through cationic bridging.