Nanobiochar for the remediation of contaminated soil and water: challenges and opportunities

Abstract

Although research on biochar has received increasing attention for environmental and agricultural applications, the significance of nanobiochar for environmental pollutant remediation is poorly understood. In contrast to bulk biochar, nanobiochar has superior physicochemical properties such as high catalytic activity, unique nanostructure, large specific surface area and high mobility in the soil environment. These unique characteristics make nanobiochar an ideal candidate for pollution remediation. Thus far, the research on nanobiochar is still in its infancy and most of the previous studies have only been conducted for exploring its properties and environmental functions. The lack of in-depth summary of nanobiochar’s research direction makes it a challenge for scientists and researchers globally. Hence in this review, we established some key fabrication methods for nanobiochar with a focus on its performance for the removal of pollutants from the environment. We also provided up-to-date information on nanobiochar’s role in environmental remediation and insights into different mechanisms involved in the pollutant removal. Although, nanobiochar application is increasing, the associated drawbacks to the soil ecosystem have not received enough research attention. Therefore, further research is warranted to evaluate the potential environmental risks of nanobiochar before large scale application. Graphical Abstract

Definitive Review of Nanobiochar

“…This property can assist in several applications, including use as an adsorbent, capacitor, reinforcing filler sensor, slow-release fertilizer, photocatalytic material, and fuel additive. 17,[38][39][40]42,43 Nanobiochar development and use have generated extensive recent interest in the scientific community as an emerging material. A few review articles summarizing nanobiochar development have appeared.…”

Hydrothermal Synthesis of Mg modified Nanobiochar from Spent Coffee Grounds for Effective Phosphate Removal: Kinetic and Isotherm Studies

“…In addition, it's not easy to get such a facility in resource‐limited areas. Compared with ball milling, hydrothermal acid digestion is a low‐temperature and effective method to produce lower‐sized NBC [14] . The strong acids used in this method perturb the microstructure of the biochar in the oxidizing hydrothermal environment which enables the production of small‐sized NBC [21] …”

“…Compared with its bulk counterpart, nanobiochar (NBC) offers a higher specific surface area, increased adsorption sites, and higher porosity. [14] These features of NBC when combined with surface modification could significantly improve the adsorption capacities of NBC. [15][16][17] For instance, Lyu and co-workers [18] demonstrated three times higher sorption capacity of thiol-modified NBC than its bulk biochar for Hg (II) removal.…”

“…Compared with ball milling, hydrothermal acid digestion is a low-temperature and effective method to produce lower-sized NBC. [14] The strong acids used in this method perturb the microstructure of the biochar in the oxidizing hydrothermal environment which enables the production of small-sized NBC. [21] Adsorption of phosphate could be one important application of NBC.…”

“…The adsorption performance of biochar can be further improved by reducing its size to the nanoscale. Compared with its bulk counterpart, nanobiochar (NBC) offers a higher specific surface area, increased adsorption sites, and higher porosity [14] . These features of NBC when combined with surface modification could significantly improve the adsorption capacities of NBC [15–17] .…”