| Activated carbons were developed from a low-cost aquatic plant residue, Lythrum salicaria L.,and tested for their ability to remove rhodamine B (RB) and ciprofloxacin hydrochloride (CPH) from aqueous solutions.The properties of carbons were investigated through Boehm’s titration method, N2 adsorption/desorption and Fourier transform infrared spectrometer (FTIR) analyses. The influence of contact time, solution pH and ionic strength on the sorption of RB and CPH was systematically studied.The dried LS was soaked in 45 wt% H3PO4 or 45 wt% H3PO4 with a certain amount of pyruvic acid (13:0.02, g H3PO4/mol PA) at a ratio of 1.3:1 (H3PO4:LS, w/w). After impregnation at a room temperature for 12h, the samples were allowed to carbonize at 450℃ and maintained for 1h in a muffle furnace under oxygen-limited conditions. The products were referred to as LSAC and PA-LSAC. PA was incorporated into LSAC as follows:LSAC (10g) was mixed with 100mL of PA solution containing 0.08 mol PA for 16h, then the carbon was separated from the solvent with a vacuum pump and washed with 500mL distilled water. This PA-modified activated carbon was referred to as LSAC-PA.Both PA-LSAC and LSAC-PA exhibited higher values of BET surface area (1128.93 and 966.55 m2/g) and total pore volume (0.841 and 0.663 cm3/g) than that of LSAC (877.11 m2/g and 0.604 cm3/g). Besides, the results of FTIR and Boehm’s titration showed that LSAC-PA contained much more surface oxygen-containing functional groups. Effects of contact time, solution pH and ionic strength on the adsorption of RB by LSAC, PA-LSAC and LSAC-PA were investigated. The adsorption amount of RB showed strong dependence on solution pH. The ionic strength had minimal effect on RB removal. The adsorption processes for RB on carbons can be represented by the pseudo-second-order kinetics model. The mechanism of the adsorption process was determined from the intraparticle diffusion model. The Langmuir model agreed well with the equilibrium adsorption data for RB sorption onto the carbons. The highest adsorption capacity derived from Langmuir model was 370.37 mg/g for LSAC,384.62 mg/g for PA-LSAC, and 333.33 mg/g for LSAC-PA. According to these results, both PA-LSAC and LSAC-PA are promising adsorbents for the removal of RB from wastewater.LS (10 g) was soaked in 45 wt% H3PO4 or 45 wt% H3PO4 with a certain amount of ferrous ammonium sulfate (10:0.001, g H3PO4/mol FAS) at a ratio of 2:1 (H3PO4:LS, w/w) for 10 h. Besides,10 g LS was firstly mixed with 0.002 mol of FAS at 100℃ for 2 h, then 45 wt% H3PO4 (20 g) was added and mixed for a further 10h. The three samples were allowed to carbonize at 450℃ in a muffle furnace for lh under oxygen-limited conditions. The products were referred to as AC, AC-FAS and AC-FAS2.Both AC-FAS and AC-FAS2 exhibited lower values of BET surface area (967.28 and 959.06 m2/g) and total pore volume (1.084 and 0.989 cm3/g) than that of AC (1327.68 m2/g and 1.414 cm3/g). Besides, the results of FTIR and Boehm’s titration showed that AC-FAS2 contains the highest amount of acidic and basic surface functional groups, while AC-FAS contains the second highest amount and AC the lowest amount. The research investigated the effect of pH and contact time on the removal of ciprofloxacin hydrochloride by AC, AC-FAS and AC-FAS2. The adsorption amount of CPH showed strong dependence on solution pH. The adsorption kinetics was best represented by the pseudo-second-order kinetics model. The mechanism of the adsorption process was determined from the intraparticle diffusion model. The equilibrium adsorption data for CPH sorption onto the carbons agreed well with the Langmuir model. According to these results, both AC-FAS and AC-FAS2 are promising adsorbents for the removal of CPH from wastewater. |
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