Converting waste lignin into nano-biochar as a renewable substitute of carbon black for reinforcing styrene-butadiene rubber

Exploring nanomaterial-modified biochar for environmental remediation applications

Environmental pollution, particularly from heavy metals and toxic elements, poses a significant threat to both human health and ecological systems. While various remediation technologies exist, there is an urgent need for cost-effective and sustainable solutions. Biochar, a carbon-rich product derived from the pyrolysis of organic matter, has emerged as a promising material for environmental remediation. However, its pristine form has limitations, such as low adsorption capacities, a relatively narrow range of pH adaptability which can limit its effectiveness in diverse environmental conditions, and a tendency to lose adsorption capacity rapidly in the presence of competing ions or organic matters. This review aims to explore the burgeoning field of nanomaterial-modified biochar, which seeks to overcome the limitations of pristine biochar. By incorporating nanomaterials, the adsorptive and reactive properties of biochar can be significantly enhanced. Such modifications, especially biochar supported with metal nanoparticles (biochar-MNPs), have shown promise in various applications, including the removal of heavy metals, organic contaminants, and other inorganic pollutants from aqueous environments, soil, and air. This review provides a comprehensive overview of the synthesis techniques, characterization methods, and applications of biochar-MNPs, as well as discusses their underlying mechanisms for contaminant removal. It also offers insights into the advantages and challenges of using nanomaterial-modified biochar for environmental remediation and suggests directions for future research.

Review on biochar as a sustainable green resource for the rehabilitation of petroleum hydrocarbon-contaminated soil

Petroleum pollution is one of the primary threats to the environment and public health. Therefore, it is essential to create new strategies and enhance current ones. The process of biological reclamation, which utilizes a biological agent to eliminate harmful substances from polluted soil, has drawn much interest. Biochars are inexpensive, environmentally beneficial carbon compounds extensively employed to remove petroleum hydrocarbons from the environment. Biochar has demonstrated an excellent capability to remediate soil pollutants because of its abundant supply of the required raw materials, sustainability, affordability, high efficacy, substantial specific surface area, and desired physical-chemical surface characteristics. This paper reviews biochar's methods, effectiveness, and possible toxic effects on the natural environment, amended biochar, and their integration with other remediating materials towards sustainable remediation of petroleum-polluted soil environments. Efforts are being undertaken to enhance the effectiveness of biochar in the hydrocarbon-based rehabilitation approach by altering its characteristics. Additionally, the adsorption, biodegradability, chemical breakdown, and regenerative facets of biochar amendment and combined usage culminated in augmenting the remedial effectiveness. Lastly, several shortcomings of the prevailing methods and prospective directions were provided to overcome the constraints in tailored biochar studies for long-term performance stability and ecological sustainability towards restoring petroleum hydrocarbon adultered soil environments.

Recent advancement of nano-biochar for the remediation of heavy metals and emerging contaminants: Mechanism, adsorption kinetic model, plant growth and development

Even though researches have shown that biochar can improve soil-health and plant-growth even in harsh environments and get rid of harmful heavy metals and new contaminants, it is still not sustainable, affordable, or effective enough. Therefore, scientists are required to develop nanomaterials in order to preserve numerous aquatic and terrestrial species. The carbonaceous chemical known as nano-biochar (N-BC) can be used to get rid of metal contamination and emerging contaminants. However, techniques to reduce hetero-aggregation and agglomeration of nano-biochar are needed that lead to the emergence of emerging nano-biochar (EN-BC) in order to maximise its capacity for adsorption of nano-biochar. To address concerns in regards to the expanding human population and sustain a healthy community, it is imperative to address the problems associated with toxic heavy metals, emerging contaminants, and other abiotic stressors that are threatening agricultural development. Nano-biochar can provide an effective solution for removal of emerging contaminants, toxic heavy metals, and non-degradable substance. This review provides the detailed functional mechanistic and kinetics of nano-biochar, its effectiveness in promoting plant growth, and soil health under abiotic stress. Nonetheless, this review paper has comprehensively illustrated various adsorption study models that will be employed in future research.

Understanding the dependence of biochar properties on different types of biomass

Owing to the diversity of biomasses and many variables in pyrolysis process, the property of biochar from varied biomass feedstock or even same biomass could differ significantly. Since the property of biochar governs the further application of biochar, this review paid particular attention to the correlation between the nature of biomass feedstock and the specifications of biochar in terms of yield, elemental composition, pH, functionalities, heating value, pore structures, morphologies, etc. The property of the biochar from the pyrolysis of cellulose, hemicellulose, lignin, woody biomass (pine, mallee, poplar, acacia, oak, eucalyptus and beech), bark of woody biomass, leaves of woody biomass, straw, algae, fruit peels, tea waste was compared and summarized. In addition, the differences of the biochar of these varied origins were also analyzed. The remaining questions, about the correlation of biomass nature with biochar characteristics, to be further investigated are analyzed in detail. The deduced information about the relationship of the nature of biochar and biomass feedstock as well as key pyrolysis parameters is of importance for further development of the methods for tailoring or production of the biochar of desirable properties. The results from this study could be interesting technically and commercially for the technology developer using biochar as the source of carbon in different applications.

Carbon Black Functionalized with Serinol Pyrrole to Replace Silica in Elastomeric Composites

Elastomer composites for dynamic mechanical applications with a low dissipation of energy are of great importance in view of their application in tire compounds. In this work, furnace carbon black functionalized with 2-2,5-dimethyl-1H-pyrrol-1-yl-1,3-propanediol (SP) was used in place of silica in an elastomer composite based on poly(styrene-co-butadiene) from solution anionic polymerization and poly(1,4-cis-isoprene) from Hevea Brasiliensis. The traditional coupling agent used for silica was also used for the CB/SP adduct: 3,3'-bis(triethoxysilylpropyl)tetrasulfide (TESPT). The composite with the CB/SP + TESPT system revealed a lower Payne effect, higher dynamic rigidity, and lower hysteresis, compared to the composite with CB + TESPT, although the latter composite had a higher crosslinking density. The properties of the silica and the CB/SP + TESPT-based composites appear similar, though in the presence of slightly higher hysteresis and lower ultimate properties for the CB/SP-based composite. The use of CB in place of silica allows us to prepare lighter compounds and paves the way for the preparation of tire compounds with lower environmental impacts.

Biochar-based materials as remediation strategy in petroleum hydrocarbon-contaminated soil and water: Performances, mechanisms, and environmental impact

Petroleum contamination is considered as a major risk to the health of humans and environment. Biochars as low-cost and eco-friendly carbon materials, have been widely used for the removal of petroleum hydrocarbon in the environment. The purpose of this paper is to review the performance, mechanisms, and potential environmental toxicity of biochar, modified biochar and its integration use with other materials in petroleum contaminated soil and water. Specifically, the use of biochar in oil-contaminated water and soil as well as the factors that could influence the removal ability of biochar were systematically evaluated. In addition, the modification and integrated use of biochar for improving the removal efficiency were summarized from the aspects of sorption, biodegradation, chemical degradation, and reusability. Moreover, the functional impacts and associated ecotoxicity of pristine and modified biochars in various environments were demonstrated. Finally, some shortcoming of current approaches, and future research needs were provided for the future direction and challenges of modified biochar research. Overall, this paper gain insight into biochar application in petroleum remediation from the perspectives of performance enhancement and environmental sustainability.

Definitive Review of Nanobiochar

Nanobiochar is an advanced nanosized biochar with enhanced properties and wide applicability for a variety of modern-day applications. Nanobiochar can be developed easily from bulk biochar through top-down approaches including ball-milling, centrifugation, sonication, and hydrothermal synthesis. Nanobiochar can also be modified or engineered to obtain "engineered nanobiochar" or biochar nanocomposites with enhanced properties and applications. Nanobiochar provides many fold enhancements in surface area (0.4-97-times), pore size (0.1-5.3-times), total pore volume (0.5-48.5-times), and surface functionalities over bulk biochars. These enhancements have given increased contaminant sorption in both aqueous and soil media. Further, nanobiochar has also shown catalytic properties and applications in sensors, additive/fillers, targeted drug delivery, enzyme immobilization, polymer production, etc. The advantages and disadvantages of nanobiochar over bulk biochar are summarized herein, in detail. The processes and mechanisms involved in nanobiochar synthesis and contaminants sorption over nanobiochar are summarized. Finally, future directions and recommendations are suggested.

Pyrrole Compounds from the Two-Step One-Pot Conversion of 2,5-Dimethylfuran for Elastomer Composites with Low Dissipation of Energy

A one-pot, two-step process was developed for the preparation of pyrrole compounds from 2,5-dimethylfuran. The first step was the acid-catalyzed ring-opening reaction of 2,5-dimethylfuran (DF), leading to the formation of 2,5-hexanedione (HD). A stoichiometric amount of water and a sub-stoichiometric amount of sulfuric acid were used by heating at 50 °C for 24 h. Chemically pure HD was isolated, with a quantitative yield (up to 95%), as revealed by 1H-NMR, 13C-NMR, and GC-MS analyses. In the second step, HD was used as the starting material for the synthesis of pyrrole compounds via the Paal-Knorr reaction. Various primary amines were used in stoichiometric amounts. 1H-NMR, 13C-NMR, ESI-Mass, and GC-Mass analyses confirmed that pyrrole compounds were prepared with very good/excellent yields (80-95%), with water as the only co-product. A further purification step was not necessary. The process was characterized by a very high carbon efficiency, up to 80%, and an E-factor down to 0.128, whereas the typical E-factor for fine chemicals is between 5 and 50. Water, a co-product of the second step, can trigger the first step and therefore make the whole process circular. Thus, this synthetic pathway appears to be in line with the requirements of a sustainable chemical process. A pyrrole compound bearing an SH group (SHP) was used for the functionalization of a furnace carbon black (CB). The functionalized CB (CB/SHP) was utilized in place of silica, resulting in a 15% mass reduction of reinforcing filler, in an elastomeric composite based on poly(styrene-co-butadiene) from solution anionic polymerization and poly(1,4-cis-isoprene) from Hevea Brasiliensis. Compared to the silica-based composite, a reduction in the Payne effect of about 25% and an increase in the dynamic rigidity (E' at 70 °C) of about 25% were obtained with CB/SHP.

Waste-derived nanobiochar: A new avenue towards sustainable agriculture, environment, and circular bioeconomy

The greatest challenge for the agriculture sector in the twenty-first century is to increase agricultural production to feed the burgeoning global population while maintaining soil health and the integrity of the agroecosystem. Currently, the application of biochar is widely implemented as an effective means for boosting sustainable agriculture while having a negligible influence on ecosystems and the environment. In comparison to traditional biochar, nano-biochar (nano-BC) boasts enhanced specific surface area, adsorption capacity, and mobility properties within soil, allowing it to promote soil properties, crop growth, and environmental remediation. Additionally, carbon sequestration and reduction of methane and nitrous oxide emissions from agriculture can be achieved with nano-BC applications, contributing to climate change mitigation. Nonetheless, due to cost-effectiveness, sustainability, and environmental friendliness, waste-derived nano-BC may emerge as the most viable alternative to conventional waste management strategies, contributing to the circular bioeconomy and the broader goal of achieving the Sustainable Development Goals (SDGs). However, it's important to note that research on nano-BC is still in its nascent stages. Potential risks, including toxicity in aquatic and terrestrial environments, necessitate extensive field investigations. This review delineates the potential of waste-derived nano-BC for sustainable agriculture and environmental applications, outlining current advancements, challenges, and possibilities in the realms from a sustainability and circular bioeconomy standpoint.

Stability and ecological risk assessment of nickel (Ni) in phytoremediation-derived biochar

Improper treatment of heavy metal-enriched biomass generated after phytoremediation might cause secondary pollution in soil and water. At present, the pyrolysis process is an effective method for the treatment of phytoremediation residue. In this study, Ni-enriched biomass was prepared using hydroponics method and further pyrolyzed at different temperatures (300-700 °C). At low pyrolysis temperatures (below 500 °C), carbonate precipitation was the main reason of Ni stabilization in biochar. Nevertheless, the formed phosphate and aluminosilicate were important factors for immobilizing Ni in biochar at high pyrolysis temperatures (above 500 °C). Moreover, the oxidizable (F3) and residual (F4) components of Ni in biochar increased with increasing pyrolysis temperature, which indicated that higher pyrolysis temperature could effectively reduce the bioavailability of Ni in biochar. The results of deionized water, acidification, oxidation, and toxic characteristic leaching procedure (TCLP) experiments showed that pyrolysis temperature was the dominant factor for Ni stabilization in biochar. The ecological risk assessments further proved that pyrolyzed Ni-enriched biochar could reduce the environmental toxicity and potential ecological risks of Ni. In the soil simulated experiment, the soil microenvironment gradually promoted the transformation of Ni in BCNiX from bioavailable fraction to stable fraction. Overall, this study would expose more reasonable reference for the long-term storage of phytoremediation residues.

Recent Advances of Lignin Functionalization for High-Performance and Advanced Functional Rubber Composites

The biomass lignin is the only large-volume renewable feedstock that is composed of aromatics but has been largely underutilized and is sought for valorization as a value-added material. Recent research has highlighted lignin as a promising alternative to traditional petrol-based reinforcements and functional additives for rubber composites. This review summarized the recent advances in the functionalization of lignin for a variety of rubber composites, as well as the compounding techniques for effectively dispersing lignin within the rubber matrix. Significant progress has been achieved in the development of high-performance and advanced functional rubber/lignin composites through carefully designing the structure of lignin-based additives and the optimization of interfacial morphologies. This Review discussed the effect of lignin on composite properties, including mechanical reinforcement, dynamic properties, antiaging performance, and oil resistance, and also the advanced stimuli-responsive performance in detail. A critical analysis for the future development of rubber/lignin composites is presented as concluding remarks.

Valorization of cellulosic fiber derived from waste biomass of constructed wetland as a potential reinforcement in polymeric composites: A technological approach to achieve circular economy

This study establishes the suitability of cellulosic fibers derived from Canna indica waste biomass for utilization as a reinforcement in natural fiber polymeric composites. The waste biomass was harvested from constructed wetlands engaged in the treatment of municipal wastewater from a gated community. The extracted Canna indica (CI) fibers were studied for their physicochemical, mechanical, structural, crystallographic, and thermal characteristics and proposed as a potential alternative to synthetic fiber. The CI fibers contained a relatively higher amount of cellulose (60 wt%) and a low wax fraction (0.5 wt%) - which is advantageous for its gainful utilization as a reinforcement. The CI fibers were thermally stable up to 237 °C and have an average fiber length, diameter, and density of 4.3 mm, 842 μm, and 0.75 g/cm³, respectively. The mean maximum tensile strength and Young's modulus were found to be 113 ± 6.82 MPa and 0.8 ± 7.91 GPa, respectively. The nano-indentation test displayed the nano hardness and modulus as 0.3 ± 0.6 GPa and 1.62 ± 0.2 GPa, respectively. The crystallographic properties of CI fibers consisted of an 87.45% crystallinity index and 3.2 nm crystallite size. The morphological attributes of CI fibers showed rough surfaces and shallow cavities on the surfaces of the fibers suggesting the suitability for its utilization as a reinforcement. It is argued that this technological approach can potentially achieve circular economy through valorization of Canna indica biomass harvested from natural wastewater treatment plants.

Nano-biochar: recent progress, challenges, and opportunities for sustainable environmental remediation

Biochar is a carbonaceous by-product of lignocellulosic biomass developed by various thermochemical processes. Biochar can be transformed into "nano-biochar" by size reduction to nano-meters level. Nano-biochar presents remarkable physico-chemical behavior in comparison to macro-biochar including; higher stability, unique nanostructure, higher catalytic ability, larger specific surface area, higher porosity, improved surface functionality, and surface active sites. Nano-biochar efficiently regulates the transport and absorption of vital micro-and macro-nutrients, in addition to toxic contaminants (heavy metals, pesticides, antibiotics). However an extensive understanding of the recent nano-biochar studies is essential for large scale implementations, including development, physico-chemical properties and targeted use. Nano-biochar toxicity on different organisms and its in-direct effect on humans is an important issue of concern and needs to be extensively evaluated for large scale applications. This review provides a detailed insight on nanobiochar research for (1) development methodologies, (2) compositions and properties, (3) characterization methods, (4) potentiality as emerging sorbent, photocatalyst, enzyme carrier for environmental application, and (5) environmental concerns.

Natural Rubber Composites Using Hydrothermally Carbonized Hardwood Waste Biomass as a Partial Reinforcing Filler- Part I: Structure, Morphology, and Rheological Effects during Vulcanization

A new generation biomass-based filler for natural rubber, 'hydrochar' (HC), was obtained by hydrothermal carbonization of hardwood waste (sawdust). It was intended as a potential partial replacement for the traditional carbon black (CB) filler. The HC particles were found (TEM) to be much larger (and less regular) than CB: 0.5-3 µm vs. 30-60 nm, but the specific surface areas were relatively close to each other (HC: 21.4 m2/g vs. CB: 77.8 m2/g), indicating a considerable porosity of HC. The carbon content of HC was 71%, up from 46% in sawdust feed. FTIR and 13C-NMR analyses indicated that HC preserved its organic character, but it strongly differs from both lignin and cellulose. Experimental rubber nanocomposites were prepared, in which the content of the combined fillers was set at 50 phr (31 wt.%), while the HC/CB ratios were varied between 40/10 and 0/50. Morphology investigations proved a fairly even distribution of HC and CB, as well as the disappearance of bubbles after vulcanization. Vulcanization rheology tests demonstrated that the HC filler does not hinder the process, but it significantly influences vulcanization chemistry, canceling scorch time on one hand and slowing down the reaction on the other. Generally, the results suggest that rubber composites in which 10-20 phr of CB are replaced by HC might be promising materials. The use of HC in the rubber industry would represent a high-tonnage application for hardwood waste.

Coconut shell and husk biochar: A review of production and activation technology, economic, financial aspect and application

The coconut industry generates a relatively large amount of coconut shell and husk biomass, which can be utilized for industrial and environmental purposes. Immense potential for added value when coconut shell and husk biomass are turned into biochar and limited studies are available, making this review paper significant. This paper specifically presents the production and activation technology, economic and financial aspect and application of biochar from coconut shell and husk biomass. Pyrolysis, gasification and self-sustained carbonization are among the production technology discussed to convert this biomass into carbon-rich materials with distinctive characteristics. The surface characteristics of coconut-based biochar, that is, Brunauer-Emmett-Teller (BET) surface area (S_BET), pore volume (V_p), pore diameter (d_p) and surface functional group can be enhanced by physical and chemical activation and metal impregnation. Due to their favourable characteristics, coconut shell and husk-activated biochar exhibit their potential as valuable adsorption materials for industrial and environmental application including biodiesel production, capacitive deionization, soil amendment, water treatment and carbon sequestration. With the knowledge of the potential, the coconut industry can contribute to both the local and global biocircular economy by producing coconut shell and husk biochar for economic development and environmental remediation. The capital and operating cost for production and activation processes must be taken into account to ensure bioeconomy sustainability, hence coconut shell and husk biomass have a great potential for income generation.

Recent advances in lignin-based carbon materials and their applications: A review

As the most abundant natural aromatic polymer, tens of million of tons of lignin produced in paper-making or biorefinery industry are used as fuel annually, which is a low-value utilization. Moreover, burning lignin results in large amounts of carbon dioxide and pollutants in the air. The potential of lignin is far from being fully exploited and the search for high value-added application of lignin is highly pursued. Because of the high carbon content of lignin, converting lignin into advanced carbon-based structural or functional materials is regarded as one of the most promising solutions for both environmental protection and utilization of renewable resources. Significant progresses in lignin-based carbon materials (LCMs) including porous carbon, activated carbon, carbon fiber, carbon aerogel, nanostructured carbon, etc., for various valued applications have been witnessed in recent years. Here, this review summarized the recent advances in LCMs from the perspectives of preparation, structure, and applications. In particular, this review attempts to figure out the intrinsic relationship between the structure and functionalities of LCMs from their recent applications. Hopefully, some thoughts and discussions on the structure-property relationship of LCMs can inspire researchers to stride over the present barriers in the preparation and applications of LCMs.

Effect of Low-Temperature Plasma Treatment on Starch-Based Biochar and Its Reinforcement for Three-Dimensional Printed Polypropylene Biocomposites

Uniform dispersion and high interfacial adhesion are two of the most difficult components of creating an ideally reinforced polymer composite. One of the solutions could be surface engineering of reinforcing filler materials utilizing innovative technologies. Low-temperature plasma treatments in the presence of sulfur hexafluoride (SF6) gas are proposed as a sustainable alternative to modify the surface properties of biochar carbon synthesized from sustainable starch-based packaging waste via a high-temperature/pressure pyrolysis reaction in the current study. X-ray photoelectron spectroscopy tests revealed that plasma treatments were effective in the fluorination of biochar carbon like wet chemical methods. By delivering fluorine-related functionalities only on the surface of the carbon, plasma treatments were efficient in changing the surface properties of biochar carbon while keeping the carbon's beneficial bulk properties intact, which is unique to this method. The modified biochar was effectively utilized to reinforce polypropylene. Mechanical properties like tensile strength improved by 91% when compared to neat polymers and 31% when compared to untreated biochar-reinforced polymers at 0.75 wt % loadings. Elongation at break increased from 12.7 to 38.78, showing an impressive 216% increase due to effective reinforcement by plasma functionalization. The decomposition onset temperature and maximum rate of decomposition temperature increased by 60 and 49 °C, respectively, when compared to neat polymers. Plasma-modified biochar-reinforced three-dimensional printed samples have shown promise to be utilized for the development of composite parts using additive manufacturing methods.

Synthesis of carbon molecular sieves from agricultural residues: Status, challenges and prospects

Adsorption is the most promising technology used in the gas separation and purification process. The key success of this technology relies on the selection of an adsorbent. Activated carbon and zeolites are the most commonly used adsorbents in the separation of particular gas from gaseous mixtures. Activated carbon deriving from fossil and biomass-based resources has wide pore size distribution and thereby results in lower selectivity. Whereas, zeolites synthesized from natural minerals are expensive which increases the cost of the purification process. Taking this into concern, the quest for synthesizing low-cost and effective adsorbents has gained greater attention in recent years. Carbon Molecular Sieves (CMSs), are considered as an attractive alternative to replace the conventional adsorbents. Furthermore, CMSs exhibit higher selectivity and adsorption capacity, due to their narrow micropore size distribution (0.3-0.5 nm). CMSs are synthesized from any organic carbonaceous precursor with low inorganic content. Since most of the agricultural residues fall under this category, they can be used as a feedstock for CMSs production. The synthesis of CMSs involves three stages: carbonization, activation, and pore modification. In this review, physicochemical characteristics of various agricultural residues, the effects of carbonization process parameters, activation methods, and pore modification techniques adopted for producing CMSs are comprehensively discussed. The effect of deposition temperature, time, and flow rate of depositing agent on pore characteristics of CMSs is briefed. The prospects and challenges in CMSs production are also studied. The insights in this review provide guidelines for synthesizing CMSs from agro-residues.

Lauric Acid Treatments to Oxidized and Control Biochars and Their Effects on Rubber Composite Tensile Properties

Biochar is a renewable source of carbon that can partially replace carbon black as filler in rubber composites. Since the carbon content of biochar is less pure than carbon black, improvements and modifications must be made to biochar to make it a viable co-filler. In this work, two methods to change the surface chemistry of biochar were employed: (1) gas treatment at 300 °C with either air or carbon dioxide, and (2) coating with lauric acid. Both methods are amenable to the current rubber processing industry. After biochar was treated with these methods, it was used as co-filler in rubber composite samples. Gas treatment with either air or carbon dioxide was found to increase stiffness in the final composites. Although lauric acid coating of biochar by itself did not have a significant effect on tensile properties, biochar that was first treated with carbon dioxide and then coated with lauric acid showed a 19% increase in tensile strength and a 48% increase in toughness. Gas treatment and lauric acid coating of biochar provide relatively simple processing techniques to improve the stiffness and tensile strength of biochar as rubber composite filler.

Turning lignin into treasure: An innovative filler comparable to commercial carbon black for the green development of the rubber industry

Driven by the global carbon neutrality action, biomass-derived functional materials have been applied in many fields to alleviate the pressure brought by the depletion of fossil energy. However, due to the complex structure, lignin faces many difficulties in its high-value utilization. The second largest biomass in the world has become the largest "natural waste". In this paper, the lignin-based biochar-silica (LB-S) hybrid nanoparticles were prepared via a combination of two-step acid precipitation and carbonization using lignin black liquor extracted from xylose residue and sodium silicate as raw materials. The effects of carbonization temperature and lignin-based biochar (LB) content on the reinforcing properties of LB-S were studied. The results show that the particle size, specific surface area, pore characteristics, and surface polarity of LB-S all affect the mechanical properties of the final vulcanizates. The reinforcement performance of the best sample (L_MB₅₀₀-S) with "high structure" characteristics can be comparable to that of commercial carbon black (CB) N550. This study shows that L_MB₅₀₀-S hybrid nanoparticles with economic benefits possess the potential to completely replace commercial CB, which can turn lignin waste into treasure and promote the green development of traditional rubber industry in the context of carbon neutrality.

Nano-biochar: A novel solution for sustainable agriculture and environmental remediation

Currently, the applications of biochar (BC) in agricultural practices and for environmental remediation purposes have demonstrated multifaceted advantages despite a few limitations. Nano-BC offers considerable opportunities especially for the remediation of hazardous contaminants as well as the improvement of crop productivity. Positive outcomes of nano-BC on soil physico-chemical and biological characteristics have indicated its suitability for agricultural applications. Nano-BC may effectively regulate the mobilization and sorption of important micro- and macro-nutrients, along with the hazardous contaminants including potentially toxic metals, pesticides, etc. Additionally, the sorption characteristics of nano-BC depends substantially on feedstock materials and pyrolysis temperatures. Nevertheless, the conducted investigations regarding nano-BC are in infant stages, requiring extensive field investigations. The nano-enhanced properties of BC on one hand dramatically improve its effectiveness and sustainability, on the other hand, there may be associated with toxicity development in diverse aquatic and/or terrestrial environments. Therefore, risk assessment on soil organisms and its indirect impact on human health is another area of concern linked with the field application of nano-BC. The present review delineates the potentiality of nano-BC as an emerging sorbent for sustainable agriculture and environmental applications.

Nanobiochar-rhizosphere interactions: Implications for the remediation of heavy-metal contaminated soils

Soil heavy metal contamination has increasingly become a serious environmental issue globally, nearing crisis proportions. There is an urgent need to find environmentally friendly materials to remediate heavy-metal contaminated soils. With the continuing maturation of research on using biochar (BC) for the remediation of contaminated soil, nano-biochar (nano-BC), which is an important fraction of BC, has gradually attracted increasing attention. Compared with BC, nano-BC has unique and useful properties for soil remediation, including a high specific surface area and hydrodynamic dispersivity. The efficacy of nano-BC for immobilization of non-degradable heavy-metal contaminants in soil systems, however, is strongly affected by plant rhizosphere processes, and there is very little known about the role that nano-BC play in these processes. The rhizosphere represents a dynamically complex soil environment, which, although having a small thickness, drives potentially large materials fluxes into and out of plants, notably agricultural foodstuffs, via large diffusive gradients. This article provides a critical review of over 140 peer-reviewed papers regarding nano-BC-rhizosphere interactions and the implications for the remediation of heavy-metal contaminated soils. We conclude that, when using nano-BC to remediate heavy metal-contaminated soil, the relationship between nano-BC and rhizosphere needs to be considered. Moreover, the challenges to extending our knowledge regarding the environmental risk of using nano-BC for remediation, as well as further research needs, are identified.

Chemical Transformation of Lignosulfonates to Lignosulfonamides with Improved Thermal Characteristics

Lignin is an abundantly occurring aromatic biopolymer that receives increasing attention as, e.g., a biofiller in polymer composites. Though its structure depends on the plant source, it is a valuable component showing biodegradability, antioxidant, and ultra-violet (UV) absorption properties. Lignosulfonates, a by-product of the paper and pulping industries formed as a result of the implementation of the sulfite process, have been used in the presented study as a raw material to obtain a sulfonamide derivative of lignin. Hereby, a two-step modification procedure is described. The obtained materials were investigated by means of FTIR, WAXD, SS-NMR, SEM, and TGA; the results of spectroscopic investigations confirm the formation of a sulfonamide derivative of lignin via the proposed modification method. The obtained modified lignin materials showed significantly improved thermal stability in comparison with the raw material. The internal structure of the lignosulfonate was not altered during the modification process, with only slight changes of the morphology, as confirmed by the WAXD and SEM analyses. The manufactured sulfonamide lignin derivatives show great promise in the potential application as an antibacterial filler in advanced biopolymeric composites.

Wet compounding with pyrolytic carbon black from waste tyre for manufacture of new tyre - A mini review

Pyrolysis offers a more focused alternative to waste tyres treatment. Pyrolytic carbon black (CBp), the main product of waste tyre pyrolysis, and its modified species can be applied to tyre manufacturing realizing its high-value utilization. Modified pyrolytic carbon black/natural rubber composites prepared by a wet compounding (WC) and latex mixing process have become an innovative technology route for waste tyre remanufacturing. The main properties and applications of CBp reported in recent years are reviewed, and the main difficulties affecting its participation in tyre recycling are pointed out. The research progress of using WC technology to replace dry mixing manufacturing of new tyres is summarized. Through literature data and comparative studies, this paper points out that the characteristic of high ash content can be well utilized if CBp is applied to tyre manufacturing. This mini-review proposes a new method for high-value utilization of CBp. The composite mixing of CBp and carbon nano-materials under wet conditions is conducive to the realization of their good dispersion in the rubber matrix. This provides a new idea for customer resource integration and connection of industry development between the tyre production industry and waste tyre disposal management.

Effect of nickel salts on the production of biochar derived from alkali lignin: properties and applications

The massive generation of alkali lignin, has aroused the attention of all walks of life, and an eco-friendly utilization approach needs to be exploited. Herein, a simple pretreatment method with nickel salts was developed for the valorisation of alkali lignin through slow pyrolysis. The pretreatment of nickel salts improved the foaming or swelling behaviors of alkali lignin upon heating, and the specific surface area and total pore size of biochars increased about thirteenfold and eighteenfold, respectively. Additionally, Ni⁰ particles were generated and embedded in the carbon matrix of biochars. The biochar from Ni(NO₃)₂ pretreated lignin catalyzed the selective hydrogenation of nitrobenzene, yielding 80.5% of aniline; and that from (CH₃COO)₂Ni pretreated lignin showed adsorption capacity of lead around 87.1 mg/g. Moreover, the NiCl₂ pretreatment contributed to the formation of 1,2-dihydroxybenzene, while Ni(SO₄)₂ was conducive to the production of 4-methylguaiacol.

Utilizing Pyrolytic Biomass Products for Rubber Reinforcement: Effect of the Silica Content in Biomass Feed Stocks

Biochar has been exploited as a substitution of carbon black in the rubber industry and various biochars exhibit diverse reinforcing abilities due to the different compositions. This work aims at studying the effect of silica on the modification process and reinforcing performance through the comparison of three biochars with different contents of silica, pyrolytic rice husks (PRH, 34 wt%), pyrolytic bamboos (PB, 7 wt%) and pyrolytic corn cobs (PC, 0.4 wt%). The results reveal that PRH requires higher rotational speed (300 min–1) than PB (200 min–1) and PC (200 min–1) to achieve similar particle sizes during the ball milling process because of the aggregations of higher silica content. Meanwhile, silica-rich pyrolytic biomass exhibits enhanced reinforcement on mechanical properties and thermal stability of rubber, and the elongation at break of vulcanizates continues to improve with increasing silica contents. Combined with the energy consumption and reinforcement, biochar containing a little amount of silica is more suitable to be widely used as bio-filler in rubber industry. This work should serve as a valuable reference to select appropriate biochar for the production of bio-fillers with high reinforcement.

Controllable conversion of biomass to lignin-silica hybrid nanoparticles: High-performance renewable dual-phase fillers

Due to the complex network of aromatic units, lignin is difficult to achieve high-value applications in the industrial field, becoming the largest "natural waste". In this paper, dual-phase fillers with excellent rubber reinforcement were prepared from lignin and sodium silicate through the method of controllable two-step acid precipitation without any complicated modification. During the formation of hybrid nanoparticles, silica nanoparticles were formed as templates in the first step, and then lignin was used as coating agent to bind with silica. The size and morphology of products could be easily adjusted by changing acid precipitation conditions. The L₆₀S_S hybrid nanoparticles with the best reinforcement performance showed the ability to replace carbon black (CB) in a high proportion. In addition, LS_RH-S hybrid nanoparticles made from rice husk black liquor had similar physical and chemical properties and excellent reinforcement properties to L₆₀S_S. Even if the ratio of each component of the raw material was different, the product could be flexibly controlled by the two-step acid precipitation to obtain the expected properties. The wide applicability of this method in many extraction processes based on alkaline procedures was proved, and it provided a basis for the process design of comprehensive utilization of biomass. This work will promote the application of lignin in high-value fields, and the sustainable development of the rubber industry by utilizing agricultural waste was achieved.

Application of typical artificial carbon materials from biomass in environmental remediation and improvement: A review

Artificial carbon materials (ACMs), notably hydrochar, pyrochar, and artificial humic substances, etc., are considered to be sustainable and eco-friendly materials for environmental remediation and improvement. At present, almost relevant literature mainly focuses on biochar, and it is necessary to systematically summarize and expand studies on ACMs. ACMs are widely used to solve pollution problems in water and soil environments, as well as to remediate and improve soil quality. This review focuses on the following issues: 1. Reveal the synthetic mechanisms and compositional reactions effects of the charring process; 2. Define artificial humus as a novel class of ACMs and discuss the application of environmental remediation and relative enhancement effects; 3. Research the relative mechanisms and significance of ACMs during remediation process, involving removal and fixation of heavy metal ions (HMs)/organic pollutants (OPs), modification of soil physicochemical properties, affecting microbial community effects, and improving fertility for crop growth. Finally, the cost-benefit analysis and security-risk evaluation of ACMs are pointed out.

Preparation and Characterization of Eco-Friendly Spent Coffee/ENR50 Biocomposite in Comparison to Carbon Black

This study investigates the impact of spent coffee biochar (Biochar) compared to carbon black (CB) as a partial replacement for carbon black in epoxidized natural rubber (ENR). Particle size and elemental analysis were used to characterize the biochar and CB. Cure characteristics, tensile, thermal, and morphological properties on the effect of biochar and CB as filler were studied. It was found that incorporating 10 phr of spent coffee biochar could improve the composites’ tensile properties and thermal performance compared to carbon black. However, the addition of biochar significantly affects the maximum torque compared to CB and delays the vulcanization time. SEM study shows that biochar has a strong effect on the morphology of composite films. The FTIR graph reveals no substantial difference between compounds with biochar and CB. According to the thermal calorimetric study, the thermal stability of ENR-Biochar is higher than that of ENR-CB. Additionally, these findings suggest that the utilization of spent coffee as a sustainable biochar could be further explored, but little has been done in epoxidized natural rubber (ENR).

Lignin derived nano-biocarbon and its deposition on polyurethane foam for wastewater dye adsorption

Historically, lignin has been produced as a waste by-product in industrial processes. In this study, lignosulfonate nanoparticles were fabricated and freeze-dried for use as a precursor material for carbonization. The use of the carbonized lignins for the adsorption of textile effluent as a value-added application is demonstrated. Characterization of the as received lignin (LN) and the developed nano-based freeze-dried lignin (NFLN) were performed prior to and after carbonization at 600, 750, 900 and 1050 °C. Using probe sonication, lignosulfonates were broken down into nanoparticles with lower weight-average molecular weight as verified by dynamic and static light scattering techniques. The difference between the LN and the NFLN was determined to be primarily morphological as the sonication and freeze-drying process imparted a platelet-like shape to the NFLN biocarbons and an increased surface area, while the remaining functionality was similar. The adsorption behaviour of methylene blue (MB), a synthetic cationic dye, was investigated using adsorption isotherm and kinetic models, with the NFLN exhibiting a maximum adsorption capacity of 109.77 mg/g. Overall, electrostatic attraction and hydrogen bonding contribute significantly to the MB adsorption. Further preliminary work was also performed demonstrating the coating of polyurethane foam for the adsorption of MB. These renewable biocarbons show promising properties for use as additive in adsorbent, coating, pigment or as a filler in polymer composite applications.

Lignin-containing polyurethane elastomers with enhanced mechanical properties via hydrogen bond interactions

In this work, lignin-containing polyester polyol (LPES) was successfully synthesized by vacuum melting method with lignin instead of polyol, and then reacted with isocyanate and chain extender to obtain lignin-based polyurethane elastomer (LPUE). The effects of lignin as reactive raw material, chain extender, and filler on the structure, thermostability, mechanical performance, and self-healing properties of elastomers were systematically studied, respectively. The comprehensive mechanical properties of the obtained materials were significantly enhanced after the introduction of lignin, especially the maximum tensile strength increased to 26.6 MPa and elongation at break reached 408.6%, which were 1510.3% and 2130.5% higher than that of the original polyurethane elastomer (PUE). Results revealed that lignin in the hard segment had a significant effect on the thermal stability and mechanical properties of polyurethane elastomer, and lignin in the soft segment had an obvious impact on the healing properties. Due to the hydrogen bonding interaction of the polar groups in the molecular chain of lignin to form a microphase-ordered structure, LPUE with excellent mechanical properties can be obtained.

Understanding the Coupling Effect between Lignin and Polybutadiene Elastomer

From an environmental and economic viewpoint, it is a win–win strategy to use materials obtained from renewable resources for the production of high-performance elastomer composites. Lignin, being a renewable biomass, was employed as a functional filler material to obtain an elastomer composite with a higher degree of mechanical performance. In the presence of a suitable coupling agent, an elevated temperature was preferred for the reactive mixing of lignin with polybutadiene rubber (BR). It is quite fascinating that the mechanical performance of this composite was comparable with carbon black-filled composites. The extraordinary reinforcing behavior of lignin in the BR matrix was understood by an available model of rubber reinforcement. In rubber composite preparation, the interfacial interaction between polybutadiene rubber and lignin in the presence of a coupling agent enabled the efficient dispersion of lignin into the rubber matrix, which is responsible for the excellent mechanical properties of the rubber composites. The rubber composites thus obtained may lead to the development of a sustainable and cost-effective end product with reliable performance. This novel approach could be implemented in other type of elastomeric materials, enabling a genuine pathway toward a sustainable globe.

Biochar for remediation of agrochemicals and synthetic organic dyes from environmental samples: A review

Application of agrochemicals in farming sector to control insects and pests; and use of synthetic organic dyes to color the products are increasing continuously due to the rapid growth of industries. During the application process many industries releases toxic agrochemicals and dyes in to the aquatic environment and on land without the proper treatment. Due to their toxicity the disposal of such chemicals is of utmost importance. Biochar offers the ability to remediate these substances from environmental matrices because of their high sorption ability of pollutants from water and soil. This review highlights the development and advancement of biochar-based treatment for abatement of agrochemicals and synthetic organic dyes, involving its technical aspects and the variables connected with removing these kinds of pollutants. Several optimization parameters like temperature, pH, chemical concentration, biochar properties, time, and co-existing ions have been elaborated. Literature survey shows that most of the researches on biochar application have been conducted in the batch mode. Hence there is an urgent need to apply this beneficial technique for the remediation of pollutants at the larger scale in the real water and soil samples. A comprehensive summary on sorption kinetics and adsorption isotherms with regards to pollutant removal is also presented. This review also covers the cost analysis of various techniques where biochar has been used as an adsorbent. Thus this review makes an easy roadmap for the further development in biochar and biochar based composites and expansion of these demanding areas of research in biochar and their applications.

Lignin Nanoparticles and Their Nanocomposites

Lignin nanomaterials have emerged as a promising alternative to fossil-based chemicals and products for some potential added-value applications, which benefits from their structural diversity and biodegradability. This review elucidates a perspective in recent research on nanolignins and their nanocomposites. It summarizes the different nanolignin preparation methods, emphasizing anti-solvent precipitation, self-assembly and interfacial crosslinking. Also described are the preparation of various nanocomposites by the chemical modification of nanolignin and compounds with inorganic materials or polymers. Additionally, advances in numerous potential high-value applications, such as use in food packaging, biomedical, chemical engineering and biorefineries, are described.

Pore Development during the Carbonization Process of Lignin Microparticles Investigated by Small Angle X-ray Scattering

Application of low-cost carbon black from lignin highly depends on the materials properties, which might by determined by raw material and processing conditions. Four different technical lignins were subjected to thermostabilization followed by stepwise heat treatment up to a temperature of 2000 °C in order to obtain micro-sized carbon particles. The development of the pore structure, graphitization and inner surfaces were investigated by X-ray scattering complemented by scanning electron microscopy and FTIR spectroscopy. Lignosulfonate-based carbons exhibit a complex pore structure with nanopores and mesopores that evolve by heat treatment. Organosolv, kraft and soda lignin-based samples exhibit distinct pores growing steadily with heat treatment temperature. All carbons exhibit increasing pore size of about 0.5-2 nm and increasing inner surface, with a strong increase between 1200 °C and 1600 °C. The chemistry and bonding nature shifts from basic organic material towards pure graphite. The crystallite size was found to increase with the increasing degree of graphitization. Heat treatment of just 1600 °C might be sufficient for many applications, allowing to reduce production energy while maintaining materials properties.

Characterization of Organosolv Birch Lignins: Toward Application-Specific Lignin Production

Organosolv pretreatment represents one of the most promising biomass valorization strategies for renewable carbon-based products; meanwhile, there is an overall lack of holistic approach to how extraction conditions affect the suitable end-usages. In this context, lignin extracted from silver birch (Betula pendula L.) by a novel hybrid organosolv/steam-explosion treatment at varying process conditions (EtOH %; time; catalyst %) was analyzed by quantitative NMR (¹H-¹³C HSQC; ¹³C NMR; ³¹P NMR), gel permeation chromatography, Fourier transform infrared (FT-IR), Pyr-gas chromatography-mass spectroscopy (GC/MS), and thermogravimetric analysis, and the physicochemical characteristics of the lignins were discussed regarding their potential usages. Characteristic lignin interunit bonding motifs, such as β-O-4', β-β', and β-5', were found to dominate in the extracted lignins, with their abundance varying with treatment conditions. Low-molecular-weight lignins with fairly unaltered characteristics were generated via extraction with the highest ethanol content potentially suitable for subsequent production of free phenolics. Furthermore, β-β' and β-5' structures were predominant at higher acid catalyst contents and prolonged treatment times. Higher acid catalyst content led to oxidation and ethoxylation of side-chains, with the concomitant gradual disappearance of p-hydroxycinnamyl alcohol and cinnamaldehyde. This said, the increasing application of acid generated a broad set of lignin characteristics with potential applications such as antioxidants, carbon fiber, nanoparticles, and water remediation purposes.

Effluents detoxification from pulp and paper industry using microbial engineering and advanced oxidation techniques

Due to the high demand of paper and related items, pulp and paper industry is flourishing day by day. With increased production, come the hazards associated with the toxic elements present in the effluents. Various microorganisms are currently employed in the remediation of these toxic effluents. In addition, various techniques like ozonation, electrocoagulation, UV treatment, Fenton's reagent, and photo-Fenton based techniques are used in advanced oxidation processes to reduce these toxins from effluents. This review highlights various above mentioned advanced techniques and innovative processes along with the biological remediation of these toxic effluents with the help of some potential microbial consortia or their combinatory effects. Moreover, the present review will also disclose the ideas on utilizing the tools of metabolic engineering, systems biology, and artificial intelligence towards microbial engineering for relatively better bioremediation processes. In the future, these techniques might be helpful in increasing the capability of microbial consortia towards detoxification of effluents to make them environmentally safe. Finally, this review gives well-synchronized approaches to get more insights into these innovative methodologies and techniques and their use for various industrial applications.

A critical review of the production and advanced utilization of biochar via selective pyrolysis of lignocellulosic biomass

Biochar is a carbon-rich product obtained from the thermo-chemical conversion of biomass. Studying the evolution properties of biochar by in-situ modification or post-modification is of great significance for improving the utilisation value of lignocellulosic biomass. In this paper, the production methods of biochar are reviewed. The effects of the biomass feedstock characteristics, production processes, reaction conditions (temperature, heating rate, etc.) as well as in-situ activation, heteroatomic doping, and functional group modification on the physical and chemical properties of biochar are compared. Based on its unique physicochemical properties, recent research advances with respect to the use of biochar in pollutant adsorbents, catalysts, and energy storage are reviewed. The relationship between biochar structure and its application are also revealed. It is suggested that a more effective control of biochar structure and its corresponding properties should be further investigated to develop a variety of biochar for targeted applications.

Devulcanization Technologies for Recycling of Tire-Derived Rubber: A Review

In general, composite materials are difficult to recycle. Tires belong to this class of materials. On top, one of their main constitutents, vulcanized rubber, is as elastomer, which cannot be remolten and hence is particularly challenging to put to a new use. Today, the main end-of-life routes of tires and other rubber products are landfilling, incineration in e.g., cement plants, and grinding to a fine powder, generating huge quantities and indicating a lack of sustainable recycling of this valuable material. True feedstock recycling is not feasible for complex mixtures such as tires, but devulcanization can be done to reactivate the cross-linked polymer for material recycling in novel rubber products. Devulcanization, i.e., the breaking up of sulfur bonds by chemical, thermophysical, or biological means, is a promising route that has been investigated for more than 50 years. This review article presents an update on the state-of-the art in rubber devulcanization. The article addresses established devulcanization technologies and novel processes described in the scientific and patent literatures. On the one hand, tires have become high-tech products, where the simultaneous improvement of wet traction, rolling resistance, and abrasion resistance (the so-called "magic triangle") is hard to achieve. On the other hand, recycling and sustainable end-of-life uses are becoming more and more important. It is expected that the public discussion of environmental impacts of thermoplastics will soon spill over to thermosets and elastomers. Therefore, the industry needs to develop and market solutions proactively. Every year, approximately 40 million tons of tires are discarded. Through the devulcanization of end-of-life tires (ELT), it is possible to produce new raw materials with good mechanical properties and a superior environmental footprint over virgin products. The devulcanization process has become an interesting technology that is able to support the circular economy concept.