Abstract
Antibiotics play on important role in controlling bacterial infections in public health. The accumulation and non-degradable of antibiotics in the environment leads contaminants and impact aquatic ecosystems. Many methods have been developed to remove antibiotics from aqueous solution. One of the most efficient and eco-friendly was the adsorption technique. The adsorption process which involves antibiotic drugs as adsorbate [Ciprofloxacin (CIP), Azithromycin (AZR) and sulfamethoxazole (SMX)] and low-cost materials of [Coconut Shell (CS) and Mallow Leaves (ML)] and their modified (carbonized, acid, base and nanocomposite) were used as adsorbent.
The chemical structure, calibration curve and λmax of each antibiotic drugs CIP, AZR and SMX which is used in this investigation; the λmax: 273 nm, 205 nm and 263 nm respectively, by using UV−vissible spectrophotometer. The physio-chemical properties such as (moisture, pH, electrical conductivity, total dissolved salt TDS and zero charge point) investigated for the prepared adsorbents. The characterization of the adsorbents and after adsorption of adsorbates were carried out by FTIR, XRD, SEM and EDX. Batch adsorption procedures for kinetic experiments were employed.
The kinetic, thermodynamic and various parameters for batch equilibrium experiments such as (initial concentration, adsorbent dosage, contact time, effect of pH and temperature) were examined for the adsorption process. The Pseudo-First-Order equation, Pseudo-Second-Order equation and Elovich as kinetic models used to describe the adsorption process while the Pseudo-Second-Order rate law was the best fit model. The isothermal models Freundlich, Langmuir and Temkin were applied at three different temperatures 298.15, 308.15 and 318.15±1 K. The values of Langmuir constant (KL) value for CIP and AZR adsorption onto the modified CS adsorbents varied between (0.011-0.180) (L mg−1) and (0.044–0.200) (L mg−1), respectively. Positive values were of each of ΔHo in the range (0.131 to 0.228) (kJ mol−l) and (0.131 to 0.228) (kJ mol−l), while ΔSo in range (0.992 to 1) (kJ mol−l K-1) and (0.992 to 1.0) (kJ mol−lK-1). The negative values of ΔGo (−18.47 to −23.74) (kJ mol−l) and (-16.819 to -23.575) (kJ mol-1) respectively, were indicating the adsorption of CIP and AZR on the adsorbents were a spontaneous and endothermic process.
The KL value for SMX adsorption onto modified ML adsornents varied between (0.014–0.250) L mg-1, while the negative values of ∆Go and ∆Ho (-20.838 to -22.518) (kJ mol-1) and (-9.897 to -14.469) (kJ mol-1), while the positive value of ΔSo (0.219-0.397) (kJ mol-1 K-1). Therefore it is indicating that the adsorption of SMX onto adsorbents were spontaneous and exothermic process.
