Bio/hydrochar Sorbents for Environmental Remediation

Abstract

An increasing global population and current societal reliance on fossil fuel resources has precipitated an ongoing crisis at the energy-materials-environment nexus. Sustainable resources are required to meet the demands of developed and emerging economies while mitigating climate change and protecting the biosphere; this has promoted the "zero-waste economy" and "trash-to-treasure strategy" concepts. [1] Achieving such ambitious goals necessitates a transition from fossil resources to renewables such as nuclear, solar, wind, and wave power, and biomass. Lignocellulosic biomass, such as agricultural and forestry residues, crops, and wood, is the most abundant (inedible to humans) biomass resource and a potential low-carbon feedstock to partially replace fossil carbon. It comprises cellulose and hemicellulose carbohydrate polymers embedded in a lignin matrix. [2] Lignin is a three-dimensional network of polyaromatic alcohols, whose upgrading can offer routes to renewable valueadded chemicals. [3] Hemicellulose comprises pentose (predominantly xylose) and hexose units connected by glycosidic bonds. Cellulose is a water insoluble, linear polysaccharide formed from glucose units linked via b-1,4-glycosidic bonds. [4] As an important renewable feedstock, biomass, and its conversion to materials, chemicals, and fuels is intensively researched. [5] Biomass conversion may occur through non-catalytic (thermo)chemical routes, e.g., pyrolysis and hydrothermal processing, and/or catalytic (bio)chemical routes, e.g., homogeneous, heterogeneous, and enzymatic catalyzed processes [3,6] (Figure 1). Bio/hydrochars are an important class of solid materials obtainable from biomass due to their applications as adsorbents and catalysts, and as precursors to activated carbons and other functional materials. [7] Bio/hydrochars and activated carbons are all pyrogenic materials, i.e., produced by thermochemical conversion and containing some organic carbon. Activated carbons may derive from any carbon source (fossil, waste, or renewable) and irrespective of sustainability concerns, whereas biochars are (now) viewed as pyrogenic materials derived from sustainably sourced biomass and not used as a fuel. [8] Activated carbons are amorphous and non-graphitic, with high surface areas and (usually) microporosity and a small proportion of hydrogen or oxygen, whereas biochars, and particularly hydrochars, often possess a higher oxygen content. A few studies refer to biochars as pyrochars (being derived by pyrolysis of biomass) and/or conflate the terms pyrochar and hydrochar under the banner of biochars. [9] In this review, we follow widely adopted literature conventions for char definitions [7c,10] : biochar is a carbon-rich, porous solid produced by biomass pyrolysis under restricted oxygen and moderate temperatures (350-700°C), whereas

Environmental Solid Waste‐derived Carbon for Advanced Rechargeable Lithium‐Sulfur Batteries: A Review

“…Increasing the pyrolysis temperature of agricultural and forestry solid wastes from 350 to 700 °C increased the surface area from 50 to 450 m 2 g À 1 for the obtained solid waste-derived carbon. [33] Consequently, various carbon materials would be obtained from the biomass such as porous carbon, activated carbon, carbon nanotubes, and graphene with an appropriate synthesis path. [34] Mostly the carbonization temperature range between 400-800 °C, sometimes reaching 1000 °C, and the activation temperature range from 600-900 °C.…”

“…Moreover, the moisture and the volatile matter contents of solid waste/biomass are removed during the thermal pyrolysis and the obtained biochar shows properties different from the bare solid waste/biomass materials. Increasing the pyrolysis temperature of agricultural and forestry solid wastes from 350 to 700 °C increased the surface area from 50 to 450 m 2 g −1 for the obtained solid waste‐derived carbon [33] . Consequently, various carbon materials would be obtained from the biomass such as porous carbon, activated carbon, carbon nanotubes, and graphene with an appropriate synthesis path [34] .…”

Titanium Carbide‐Based Adsorbents for Removal of Heavy Metal Ions and Radionuclides: From Nanomaterials to 3D Architectures

“…Hydrochar and biochar compounds produced from agricultural and forestry wastes have abundant surface chemical functional groups and are ideal materials for adsorbing toxic metal pollutants. [ 42,117 ] Dong et al successfully synthesized “hydrochar‐wrapped Ti 3 AlC 2 ‐derived nanofibers” (HCTNFs) through a one‐pot hydrothermal reaction using economical and green glucose, cellulose, and pine sawdust as precursors. HCTNFs are the best adsorbents compared with activated carbon and Ti 3 AlC 2 in adsorption tests for removing Cd(II) and Cu(II) from the aqueous solution.…”

“…[ 28 ] Adsorption methods are widely used to remove pollutants from water. [ 29 ] Over the years, scientists have focused on a large array of materials for adsorption applications such as graphene, [ 30 ] MoS 2 , [ 31 ] transition metal carbides, [ 32 ] g‐C 3 N 4 , [ 33 ] covalent organic frameworks (COFs), [ 34 ] metal organic frameworks (MOFs), [ 35 ] zeolitic imidazolate frameworks, [ 36 ] clay minerals, [ 37 ] layered double hydroxides (LDHs), [ 38 ] aerogels, [ 39 ] metal oxides, [ 40 ] active carbons, [ 41 ] ordered mesoporous carbon, [ 42 ] polymers, [ 43 ] and graphene oxide (GO) [ 44 ] as adsorbents to separate HMIs and radionuclides. [ 45 ] However, these materials have some shortcomings: 1) COFs and MOFs are not stable in complex wastewater; 2) LDHs exhibit slow adsorption kinetics and limited selectivity; 3) the synthesis process of GO and C 3 N 4 are complicated and expensive.…”

Applying ANFIS and LSSVM Models for the Estimation of Biochar Aromaticity

“…By undergoing biomass thermochemical transformation throughout an oxygen-scarce condition, biochar is created [1,2]. As a carbon-negative product and an efficient way to enhance soil productivity, biochar has lately gained attention [3][4][5].…”