Effect of pyrolysis temperature of coconut fibre biochar incorporated in Zn/Al layered double hydroxide for the removal of nickel(II).

Abstract

Coconut-fiber biochar (CCFB) pyrolyzed at different pyrolysis temperatures (400°C, 500°C, and 600°C) that immobilized Zn/Al layered double hydroxides (Zn/Al LDH-CCFB) composite adsorbent was prepared via a simple co-precipitation technique. The composite adsorbents were used to reduce the high concentration of Ni(II) metal ions from aqueous solution. The morphological analysis was investigated scanning electron microscopy (SEM). A series of batch adsorption tests was conducted with different parameters, which cover the pH of the solution (3-7), initial concentration of Ni(II) (10-250 mg/L), and contact time of the shaking time (0.16-8 h). Pseudo-second order kinetic model was well fitted for all of the samples, compared to pseudo-first order and intraparticle diffusion kinetic models, with the value of R2 = 0.9993, 0.9719, 0.9924, and 0.9978 for Zn/Al LDH-0, Zn/Al LDH-CCFB400, Zn/Al LDH-CCFB500, and Zn/Al LDH-CCFB600, respectively. Meanwhile, the adsorption process was best described by the Freundlich model with the value of R2 = 0.9311, 0.9987, 0.9843, and 0.9981 for Zn/Al LDH-0, Zn/Al LDH-CCFB400, Zn/Al LDH-CCFB500, and Zn/Al LDH-CCFB600, respectively. From the adsorption performance test, it was found that the adsorption capacity of Zn/Al LDH-CCFB500 that was agitated for 4 h at pH 7 was higher compared with other samples, demonstrating an adsorption capacity of up to 106.95 mg/g. The adsorption capacity of all of the Zn/Al LDH-CCFB had improved, compared to pristine Zn/Al LDH-0. Thus, it is concluded that Zn/Al LDH-CCFB possesses a great potential for the adsorbent in the removal of pollutants, especially the hazardous heavy metal ions.