water pollution and pollutants are an important issue and a major concern all over the world. Different pollutions have posed great dangers to the human communities and the ecosystem health [۱,۲]. Layered double hydroxides (LDHs) are two-dimensional layered anionic clays That have received much attention due to their excellent physical and chemical properties. Their public formula is [M۱-x۲+Mx۳+(OH)۲] (An-)x/n-mH۲O; M۲+, M۳+ and An- demonstrate divalent and trivalent cations, and the interlayer anion respectively [۳,۴]. The important properties of LDHs that leading to their abundant applications in the field of adsorption are: ۱) their structural resistance to water, ۲) their significant porosityand big space between layers, and ۳) the presence of a large number of replaceable anions between the positively charged layers [۵].
Activated carbon (AC) is one of the known adsorbents for different types of contamination due to its porous structure and large surface area [۶]. The combination of carbon nanomaterials (e.g., graphene, carbon dot, activated carbon, etc.) and layered double hydroxides leads to the creation of efficient nanocomposites with excellent properties as many properties of these two substances can complement each other [۷]. In this study, MgAl LDH/activated carbon (LDH/AC) nanocomposite as an eco-friendly adsorbent was synthesized successfully through a co-precipitation method and used for the removal of tetracycline (TC) antibiotics from aqueous solutions. The materials were characterized by X-ray diffraction (XRD) and FTIR spectroscopy. The effect of different parameters on the sorption process such as pH, adsorbent dose, contacting time, and initial concentration of TC was investigated.
Central composite design (CCD) under response surface methodology (RSM) was utilized to determine the optimal conditions for TC antibiotic removal. Also, a statistically adequate model based on CCD was obtained to describe the effect of the variables on each other and operating variables on the sorption process. The optimum conditions of removal of TC antibiotic were pH=۵.۱, adsorbent amount: ۰.۱۱ g, initial antibiotic concentration: ۵۰ mg/L, and contact time: ۹۰ min. Under optimal conditions, about ۹۱% of tetracycline was removed via LDH/AC adsorbent. Compared with the LDH and activated carbon pure, the as-prepared adsorbent showed a better performance towards the elimination of tetracycline.