Magnesium Oxide Embedded Nitrogen Self-Doped Biochar Composites: Fast and High-Efficiency Adsorption of Heavy Metals in an Aqueous Solution

Abstract

Lead (Pb) pollution in natural water bodies is an environmental concern due to toxic effects on aquatic ecosystems and human health, while adsorption is an effective approach to remove Pb from the water. Surface interactions between adsorbents and adsorbates play a dominant role in the adsorption process, and properly engineering a material's surface property is critical to the improvement of adsorption performance. In this study, the magnesium oxide (MgO) nanoparticles stabilized on the N-doped biochar (MgO@N-biochar) were synthesized by one-pot fast pyrolysis of an MgCl-loaded N-enriched hydrophyte biomass as a way to increase the exchangeable ions and N-containing functional groups and facilitate the adsorption of Pb. The as-synthesized MgO@N-biochar has a high performance with Pb in an aqueous solution with a large adsorption capacity (893 mg/g), a very short equilibrium time (<10 min), and a large throughput (∼4450 BV). Results show that this excellent adsorption performance can be maintained with various environmentally relevant interferences including pH, natural organic matter, and other metal ions, suggesting that the material may be suitable for the treatment of wastewater, natural bodies of water, and even drinking water. In addition, MgO@N-biochar quickly and efficiently removed Cd and tetracycline. Multiple characterizations and comparative tests have been performed to demonstrate the surface adsorption and ion exchange contributed to partial Pb adsorption, and it can be inferred from these results that the high performance of MgO@N-biochar is mainly due to the surface coordination of Pb and C═O or O═C-O, pyridinic, pyridonic, and pyrrolic N. This work suggests that engineering surface functional groups of biochar may be crucial for the development of high performance heavy metal adsorbents.

Application of biochar-based materials in environmental remediation: from multi-level structures to specific devices

“…In a study about magnetic biochar for mercury removal, it was found that Fe 3+ in tetrahedral coordination contributes to mercury adsorption on the biochar (Yang et al 2016b). For the sorption of some heavy metals, ion exchange may also play an important role in the sorption of biochar (Ling et al 2017).…”

Risk Evaluation of Pyrolyzed Biochar from Multiple Wastes

“…Modified biochar produced with acid, base, and oxidation treatment that supported zero-valent iron nanoparticles improved the removal of Cr(VI) using acid treated biochar, owing to the large surface area, low surface negative charge, and low pH [148]. Magnesium oxide nanoparticles stabilized on N-doped biochar synthesized by fast pyrolysis (400-600°C) resulted in a high Pb adsorption capacity in short equilibrium time (<10 min) and a large material through the system including removal of Cd 2+ and tetracycline [149]. Modified biochar through activation has demonstrated great sorption efficiency of HMs.…”

“…Modified biochar with magnet (hematite) and NaOH are cheap sources to enhance biochar properties and create friendly environmental substitute adsorbent in the removal of As contaminant using external magnet, and HMs (Pb 2+ , Cd 2+ , Cu 2+ , Zn 2+ , Ni 2+ ) [40,54]. Magnesium oxide nanoparticles on N-doped biochar is suitable for Pb adsorption and the removal of Cd 2+ and tetracycline in various environment obstructions (pH, natural organic matter, and metal ions), thus its suitability in the treatment of wastewater, natural water resources, and drinking water [149]. Similarly, modified and efficient zero-valent iron nanoparticles methods are cost effective.…”

A scientometric review of biochar research in the past 20 years (1998–2018)

“…The research hotspots were transformed to competitive sorption between heavy metals (Deng et al 2017;Park et al 2016a), organic and heavy metals co-contamination removal (Frankel et al 2016;Zhou et al 2017b). An increasing research interest focused on the activated or modified biochar, which exhibited extremely high sorption efficiency for heavy metals (Deng et al 2018b;Ding et al 2016;Li et al 2017a;Ling et al 2017;Liu et al 2016;Niu et al 2017;Trakal et al 2016;Wu et al 2017b). Among the heavy metals, Cd immobilization by biochar was most studied, which could be seen from the relatively big ring in Fig.…”

“…The research about biochar remediation for heavy metals/metalloids contamination is well documented (Beesley and Marmiroli 2011; Cao et al 2009;Chen et al 2016;Lu et al 2012b;Qian et al 2017;Trakal et al 2014). With deeper understanding, the structures and surface properties of biochar have been modified with diverse methods, which deserves an increased attention globally (Chen et al 2011;Creamer et al 2018;Deng et al 2017Deng et al , 2018aLing et al 2017;Son et al 2018;Yao et al 2013;Zhang et al 2013a).…”