Preparation Of Enteromorpha Prolifera-based Surfactant-doped Activated Carbon And Its Application For Ni²⁺and Ciprofloxacin Removal

Enteromorpha prolifera was employed as precursor to prepare activated carbon (EPAC) by H3PO4activation. Two surfactants (cetyl trimethyl ammonium bromide--CTAB and sodium benzenesulfonate-SBS) were used to modify activated carbon during H3PO4activation, producing EPAC-CTAB and EPAC-SBS. NaOH solution was employed in regeneration of ciprofloxacin (C1P)-loaded EPAC and EPAC-SBS to obtain REPAC and REPAC-SBS. The physicochemical properties of these activated carbons were characterized by scanning electron microscopy (SEM), N2adsorption/desorption isotherms, Fourier transform infrared spectroscopy (FTIR), Boehm titration and X-ray photoelectron spectroscopy (XPS). Batched adsorption studies were carried out to compare the Ni2+and CIP adsorption behaviors of these carbons. The effects of experimental parameters, such as contact time, initial concentration, pH, temperature and ionic strength the adsorption performance were investigated. The adsorption kinetics isotherm and thermodynamics were used to analyze the adsorption process and gain insights into adsorption mechanisms.The characterization results showed that EPAC-CTAB (689.0m2/g and0.361cm3/g) and EPAC-SBS (738.0m2/g and0.924cm3/g) exhibited smaller surface area and lower total pore volume than those of EPAC (1045.8m2/g and1.048cm3/g). The results of FTIR and Boehm titration showed modified activated carbons were characteristic of more surface functional groups than EPAC, especially acidic functional groups. Adsorption of Ni2+on EPAC and EPAC-CTAB exhibited a strong pH-dependent behavior and adsorption capacity increased with the increasing solution pH, while adsorption capacity of CIP on EPAC and EPAC-SBS increased firstly and then decreased as pH increased. The ionic strength had an influence on adsorption and adsorption capacity reduced with the increasing ionic strength.The maximum adsorption capacity of Ni2+determined from the Langmuir model was16.9mg/g for EPAC and49.8mg/g for EPAC-CTAB, while adsorption of CIP on EPAC (285.7mg/g) and EPAC-SBS (238.1mg/g) and regeneration effects of NaOH solution were high (85.84%and89.74%). The adsorption of Ni2+on EPAC and EPAC-CTAB were examined and agreed well with the pseudo-second-order model. The Ni2+and CIP adsorption isotherms data were well represented by Langmuir model. The thermodynamic parameters for adsorption of CIP on EPAC, EPAC-SBS, REPAC and REPAC-SBS represented that the adsorption process had been confirmed to be spontaneous and endothermic reactions.