Abstract
This study presents the modification of cassava root husk-derived biochar (CRHB) with ZnO nanoparticles (ZnO-NPs) for the simultaneous adsorption of As(iii), Cd(ii), Pb(ii) and Cr(vi). By conducting batch-mode experiments, it was concluded that 3% w/w was the best impregnation ratio for the modification of CRHB using ZnO-NPs, and was denoted as CRHB-ZnO3 in this study. The optimal conditions for heavy metal adsorption were obtained at a pH of 6–7, contact time of 60 min, and initial metal concentration of 80 mg L−1. The heavy metal adsorption capacities onto CRHB-ZnO3 showed the following tendency: Pb(ii) > Cd(ii) > As(iii) > Cr(vi). The total optimal adsorption capacity achieved in the adsorption of the 4 abovementioned metals reached 115.11 and 154.21 mg g−1 for CRHB and CRHB-ZnO3, respectively. For each Pb(ii), Cd(ii), As(iii), and Cr(vi) metal, the maximum adsorption capacities of CRHB-ZnO3 were 44.27, 42.05, 39.52, and 28.37 mg g−1, respectively, and those of CRHB were 34.47, 32.33, 26.42 and 21.89 mg g−1, respectively. In terms of kinetics, both the pseudo-first-order and the pseudo-second-order fit well with metal adsorption onto biochars with a high correlation coefficient of R2, while the best isothermal description followed the Langmuir model. As a result, the adsorption process of heavy metals onto biochars was chemisorption on homogeneous monolayers, which was mainly controlled by cation exchange and surface precipitation mechanisms due to enriched oxygen-containing surface groups with ZnO-NP modification of biochar. The FTIR and EDS analysis data confirmed the important role of oxygen-containing surface groups, which significantly contributed to removal of heavy metals with extremely high adsorption capacities, comparable with other studies. In conclusion, due to very high adsorption capacities for metal cations, the cassava root husk-derived biochar modified with ZnO-NPs can be applied as the alternative, inexpensive, non-toxic and highly effective adsorbent in the removal of various toxic cations.
Highlights
Trivalent arsenic (As(III)), lead (Pb), cadmium (Cd), and hexavalent chromium (Cr(VI)) are natural constituents existing in soils, groundwater, and surface water sources.[1,2] Due to their toxicity, media containing these metals excessively are considered contaminated.[3]
Based on knowledge obtained from literature studies, this study aims to four primary speci c targets: (1) fabricating the biochar adsorbent from wasted cassava root husk (CRH) by pyrolysis process; (2) modifying the original adsorbent by loading zinc oxide (ZnO) nanoparticles on CRHderived biochar; (3) evaluating the environmental parameters that affect the adsorption of heavy metals in aqueous solution; and (4) simulating the adsorption behaviors of both pristine and modi ed biochars through typical adsorption isothermal and kinetic models
This study examined four types of CRH-based adsorbents, corresponded with four impregnation ratios applied on the loading of Zinc oxide nanoparticles (ZnO-NPs) onto cassava root husk-derived biochar
Summary
Trivalent arsenic (As(III)), lead (Pb), cadmium (Cd), and hexavalent chromium (Cr(VI)) are natural constituents existing in soils, groundwater, and surface water sources.[1,2] Due to their toxicity, media containing these metals excessively are considered contaminated.[3] aqueous environments are likely the most prevalent source of heavy metal contamination because humans directly consume water or foods containing heavy metals from water.[4] More. They can alter hereditary materials like DNA, causing unwanted harmful mutations to the suffering bodies and, possibly, their descendants.[13,14,15,16] Besides, does heavy metal contaminated water affect humanity, it in icts negative impacts to ecosystems as well.[10,12,17]
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