Banana stem and leaf biochar as an effective adsorbent for cadmium and lead in aqueous solution

Abstract

Lead (Pb) and cadmium (Cd) are toxic heavy metals commonly found in aqueous environments. Biochar as a green adsorbent generated from biomass feedstock may be used for effective removal of these heavy metals. This study investigated the adsorption kinetics and isotherms of Pb2+ and Cd2+ in aqueous solutions at different pH by biochar prepared from banana stem and leaf (BSL-BC) at 400 °C. Characterizations using scanning electron microscope, X-ray diffraction, and Fourier-transform infrared spectroscopy showed that the synthesized BSL-BC had rough surface, porous structure, and oxygen-containing functional groups. The adsorption of Pb2+ and Cd2+ onto BSL-BC reached equilibrium in 8 h and 200 min, respectively, with faster adsorption attained at higher pH and the optimum pH occurred at 5 (Pb2+) and 8 (Cd2+). All adsorption kinetic data followed the pseudo-second-order rate model. The adsorption isotherm data of Pb2+ and Cd2+ could be well-described by the Langmuir and Freundlich models, respectively, whereas neither the Temkin or Dubinin–Radushkevich models provided satisfactory fitting results. The maximum adsorption capacities for Pb2+ and Cd2+ were 302.20 and 32.03 mg/g, respectively. The calculated mechanism contributions showed that complexation with oxygen-containing functional groups, ion exchange, mineral precipitation, and Pb2+/Cd2+-π coordination accounted for 0.1%, 8.4%, 88.8%, and 2.6% to Pb2+ adsorption, and 0.4%, 6.3%, 83.0%, and 10.4% to Cd2+ adsorption, respectively. Therefore, mineral precipitation was likely the major mechanism responsible for adsorption of both Pb2+ and Cd2+ by BSL-BC. The results suggest that the synthesized BSL-BC has great potential for adsorption of Pb2+ and Cd2+ from aqueous solutions.

Effective removal of Pb(II) ions using piperazine-modified magnetic graphene oxide nanocomposite; optimization by response surface methodology

“…Since the Langmuir model provided the best fit on Pb 2+ adsorption by Pip@MGO (Supplementary Fig. S2 ), the above result indicates that monolayer adsorption of Pb(II) occurred at homogeneous sites with equal energy on nanocomposite adsorbent 60 . Moreover, the maximum adsorption capacity ( q max ) of Pip@MGO nanocomposite for Pb(II) reached 558.2 mg g −1 and it helps the fact that the proposed adsorbent has a high surface area, especially in the nano proportions.…”

“…As the initial Pb(II) aqueous concentration ( C 0 ) increased from 50 to 600 mg L −1 , Q e increased from 64.3 to 525.7 mg g −1 . Since lead could be classified as a hard Lewis acid, the amine, hydroxyl and carboxyl groups (hard Lewis bases) on the adsorbent probably have a higher affinity for Pb 60 .…”

Phosphoric acid surface modified Moringa oleifera leaves biochar for the sequestration of methyl orange from aqueous solution: Characterizations, isotherm, and kinetics analysis

“…Both raw and activated biochar demonstrated two‐phase sorption, e.g., high sorption initial phase and low sorption later phase, which is identical to other reported biochars for the sequestration of different dye and metal species (Chu et al, 2020; Kwak et al, 2019; Zeghioud et al, 2022). In the initial phase, the biochar surface has abundant active sites (Liu et al, 2022), promoting the interaction of pollutants molecules with the sorption sites (Roy et al, 2022); these sites become saturated with time, leading to decreasing sorption of MO molecules (Aichour et al, 2022).…”

“…(Kwak et al, 2019; Shaheen et al, 2019), agricultural wastes (e.g., rice straw, coffee waste, canola straw, agricultural peels) (Islam et al, 2021; Kwak et al, 2019; Wijitkosum, 2022), municipal and industrial sludges (Chanaka Udayanga et al, 2019; Tarelho et al, 2020), and animal wastes (Kwak et al, 2019; Rehman et al, 2020) under low or no oxygen conditions (Huang et al, 2021). Recently, leaf‐based feedstocks have received increased attention because these materials are available in large quantities throughout the world, are cheap, and have been unused in many cases (Liu & Li, Chen, et al, 2022; Ma et al, 2019; Sahota et al, 2018). In addition, the leaf‐based biochars have excellent adsorption capacity to remove both organics and inorganics because of the presence of a higher number of oxygen‐containing surface functional groups such as phenol, hydroxyl, carboxyl, lactol, lactone, amino, nitro, and quinone (Jeirani et al, 2017; Ma et al, 2019).…”

Replacement of biochar from waste for cement: mechanisms and eco-benefits

“…The benefits associated with the pyrolysis are huge, which include mass reduction, odour removal, pathogen killing, heavy metal fixation, thorough elimination of environmental hormones and energy recovery in the form of gas and oil 16 . The products of the pyrolysis of municipal sludge (PPMS) and domestic garbage (PPDG) can be used as fertilizers to apply to cropland, and as the adsorbents of heavy metals and organic pollutants to apply to soil remediation and the treatment of polluted water 17,18 . PPMS and PPDG applied with different ways are also considered as a carbon sink 19 .…”