Magnetic hybrid chitin-horse manure humic acid for optimized Cd(II) and Pb(II) adsorption from aquatic environment
Basuki Rahmat, Yusuf Bramastya Apriliyanto, Elva Stiawan, Adya Rizky Pradipta, Bambang Rusdiarso, Budi Riza Putra
Abstract
Hybrid magnetic-humic acid-chitin (HMHA-Ch-Fe 3 O 4 ) was successfully prepared from horse manure and crab shell waste as economical and green adsorbent for Cd(II) and Pb(II). The success synthesis of HMHA-Ch-Fe 3 O 4 was confirmed by diverse instrument. The FT-IR study showed that the HMHA-Ch-Fe 3 O 4 had the combination of characteristics peaks of HMHA, chitin, and Fe 3 O 4 . Based on Brunauer, Emmett, and Teller's (BET) theory, the HMHA-Ch-Fe 3 O 4 specific surface area (52.26 m 2 /g) was higher than original HMHA (35.71 m 2 /g). The average pore size of HMHA-Ch-Fe 3 O 4 (7.33 nm) was within the mesoporous range (2–50 nm). HMHA-Ch-Fe 3 O 4 ferromagnetism was exhibited by the vibrating sample magnetometer (VSM), which determined magnetic saturation (Ms) at 40.70 emu/g. Applicability of HMHA-Ch-Fe 3 O 4 was thoroughly investigated in batch experiments using an aqueous solution. Four isotherm (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich (DR)) and six kinetic models (Lagergren, Ho, Santosa, Rusdiarso-Basuki-Santosa (RBS), Elovich, and Intraparticle Diffusion) were conducted to investigate the mechanism of Pb(II) and Cd(II) adsorption on HMHA-Ch-Fe 3 O 4 . Among the models, DR isotherm model and Ho kinetics models were found to be more suitable than others for Cd(II) and Pb(II) adsorption reactions. With correlation coefficient (R 2 = 0.9989 for Cd(II) and R 2 = 0.9985 for Pb(II)), the DR model indicates multilayer adsorption of 288.72 mg/g Cd(II) and 782.95 mg/g Pb(II) on HMHA-Ch-Fe 3 O 4 surface. The maximum monolayer adsorption deduced by Langmuir isotherm model of 95.55 mg/g and 127.94 mg/g for Cd(II) and Pb(II), respectively. The kinetic correlation coefficient (R 2 = 0.9998 for Cd(II) and R 2 = 0.9989 for Pb(II)) of the Ho kinetics model indicates that the Cd(II) and Pb(II) adsorption onto magnetite was dominated by chemisorption. In addition, up to five adsorption-desorption cycles, the Cd(II) and Pb(II) adsorption was 84.29 % and 88.71 %, respectively. By the eluent 0.1 M HNO 3, desorption of Cd(II) and Pb(II) from the adsorbent surface was 93.87 % and 90.71 %, respectively, demonstrating enhanced recycling potential and cost-effectiveness. Moreover, the feasibility and cost-effectiveness study broaden their applicability as environment-friendly adsorbents for Cd(II) and Pb(II) uptake from aquatic environment.