Biochar from byproduct to high value added material – A new adsorbent for toxic metal ions removal from aqueous solutions

Advancements in Biomass-Derived Activated Carbon for Sustainable Hydrogen Storage: A Comprehensive Review

The increasing global energy demand, which is being driven by population growth and urbanization, necessitates the exploration of sustainable energy sources. While traditional energy generation predominantly relies on fossil fuels, it also contributes to alarming CO2 emissions. Hydrogen has emerged as a promising alternative energy carrier with its zero-carbon emission profile. However, effective hydrogen storage remains a challenge. When exposed to hydrogen, conventional metallic vessels, once considered to be the primary hydrogen carriers, are prone to brittleness-induced cracking. This has spurred interest in alternative storage solutions, particularly porous materials like metal-organic frameworks and activated carbon (AC). Among these, biomass-derived AC stands out for its eco-friendly nature, cost-effectiveness, and optimal adsorption properties. This review offers a comprehensive overview of recent advancements in the synthesis, characterization, and hydrogen storage capabilities of AC. The unique benefits of biomass-derived sources are highlighted, as is the pivotal role of chemical and physical activation processes. Furthermore, we identify existing challenges and propose future research directions in AC-based hydrogen storage. This compilation aims to serve as a foundation for potential innovations in sustainable hydrogen storage solutions.

A Critical Review of Snail Shell Material Modification for Applications in Wastewater Treatment

Sea material is becoming increasingly popular and widely used as an adsorbent in wastewater treatment. Snail shell, a low-cost and natural animal waste material, has been shown to have a high calcium content (>99%) and a large potential surface area for the development of sustainable adsorbents. This paper presents a novel synthesis of methods for using snail shell absorbent materials in the treatment of wastewater containing heavy metals, textile dyes, and other organic substances. Modified biochar made from snail shells has gained popularity in recent years due to its numerous benefits. This paper discusses and analyzes modification methods, including impregnating with supplements, combining other adsorbents, synthesis of hydroxyapatite, co-precipitation, and the sol-gel method. The analysis of factors influencing adsorption efficiency revealed that pH, contact time, temperature, initial concentration, and adsorbent dose all have a significant impact on the adsorption process. Future research directions are also discussed in this paper as a result of presenting challenges for current snail adsorbents.

Hydrocarbons removal from synthetic bilge water by adsorption onto biochars of dead Posidonia oceanica

Bilge waters are wastewaters produced on boats during navigation and usually contain hydrocarbons and oils. They cannot be directly released into the sea if not below a hydrocarbons concentration limit set by current legislation. Appropriate oil in water separator (OWS) systems can be installed on board boats to remove hydrocarbons from bilge water allowing their spillage into the sea. These systems may contain an adsorption step on a suitable adsorbent. Here, biochars produced from pyrolysis of dead Posidonia oceanica, pristine or chemically activated, have been tested as hydrocarbons adsorbents. Adsorption experiments with aqueous dispersions simulating bilge waters containing a marine gas oil (MGO) fuel for boats, a surfactant, and different NaCl concentrations were carrying out. The hydrocarbons concentrations before and after adsorption have been directly measured by using the reverse phase HPLC technique coupled with a fluorescence detector. These measurements are very fast and their reliability was verified by re-measuring the hydrocarbons concentrations of some samples with the GC-MS-MS technique, according to one of the traditional methods for hydrocarbons determination in emulsions. Different isotherm equations were used to fit the adsorption data. The biochars were characterized from the chemical-structural point of view by means of several instrumental techniques.

Multifunctional Loblolly Pine-Derived Superactivated Hydrochar: Effect of Hydrothermal Carbonization on Hydrogen and Electron Storage with Carbon Dioxide and Dye Removal

Pore modulation via hydrothermal carbonization (HTC) needs investigation due to its crucial effect on surface that influences its multirole utilization of such ultraporous sorbents in applications of energy storage- hydrogen and capacitive- as well as for pollutant abatement- carbon capture and dye removal. Hence, loblolly pine was hydrothermally carbonized followed by KOH activation to synthesize superactivated hydrochars (SAH). The resulting SAHs had specific surface area (SSA) 1462-1703 m²/g, total pore (TPV) and micropore volume (MPV) of 0.62-0.78 cm³/g and 0.33-0.49 cm³/g, respectively. The SAHs exhibit excellent multifunctional performance with remarkably high atmospheric CO₂ capture of 145.2 mg/g and high pressure cryogenic H₂ storage of 54.9 mg/g. The fabricated supercapacitor displayed substantial specific capacitance value of maximum 47.2 Fg^-1 at 1 A g^-1 in 6 M KOH and highest MB dye removal of 719.4 mg/g. Higher HTC temperature resulted in increased surface porosity as higher SSA, TPV benefitted H₂ storage and MB dye removal while superior MPV favored CO₂ capture. Moderate HTC temperature ensured higher mesopore-to-macropore volume ratio favoring electrochemical performance. Isotherm modelling of the adsorbates was compared using models: Langmuir, Freundlich, Langmuir- Freundlich and Temkin.

Revalorization of Posidonia oceanica Waste for the Thermochemical Production of Biochar

Every year, many tonnes of Posidonia oceanica are removed from Mediterranean beaches to maintain the quality and pleasure of use of the beaches. Most of this waste ends up in landfills, entailing removal costs. In this work, the Posidonia oceanica material was characterised, and a washing system was developed to obtain biochar. An adequate washing of the starting biomass was shown to play a key role as it led to an over 90% salt content reduction and, therefore, a decrease in conductivity values. The use of biochar as a soil remediator improves soil properties, carbon sequestration, and plant growth. However, not all types of biochars are suitable for this type of application. Therefore, the properties of biochar made from Posidonia Oceanica at different temperatures (300, 400, and 500 °C) were studied. All the biochars obtained showed to exceed 10% organic carbon, which is the lower limit to be applied to soils, the maximum percentage having been obtained at 300 °C. In addition, all presented pH values (8.02, 10.32, and 10.38 for the temperatures of 300, 400, and 500 °C, respectively) that were similar to those of other effective biochars for the remediation of acid soils.

Artificial intelligence (AI) applications in adsorption of heavy metals using modified biochar

The process of removal of heavy metals is important due to their toxic effects on living organisms and undesirable anthropogenic effects. Conventional methods possess many irreconcilable disadvantages pertaining to cost and efficiency. As a result, the usage of biochar, which is produced as a by-product of biomass pyrolysis, has gained sizable traction in recent times for the removal of heavy metals. This review elucidates some widely recognized harmful heavy metals and their removal using biochar. It also highlights and compares the variety of feedstock available for preparation of biochar, pyrolysis variables involved and efficiency of biochar. Various adsorption kinetics and isotherms are also discussed along with the process of desorption to recycle biochar for reuse as adsorbent. Furthermore, this review elucidates the advancements in remediation of heavy metals using biochar by emphasizing the importance and advantages in the usage of machine learning (ML) and artificial intelligence (AI) for the optimization of adsorption variables and biochar feedstock properties. The usage of AI and ML is cost and time-effective and allows an interdisciplinary approach to remove heavy metals by biochar.

Lead(II) ions adsorption onto amyloid particulates: An in depth study

The production of new cost-effective biocompatible sorbent sustainable materials, with natural origins, able to remove heavy metals from water resources is nowadays highly desirable in order to reduce pollution and increase clean water availability. In this context, self-assembled protein materials with amyloid structures seem to have a great potential as natural platform for a broader development of highly-tunable structures. In this work we show how protein particulates, a generic form of protein aggregates, with spherical micro sized shape can be used as adsorbents of Pb²⁺ ions from aqueous solution. The effect of pH, ionic medium, ionic strength and temperature of the metal ion solution on the adsorption ability and affinity has been evaluated revealing the complexity of adsorption mechanisms which are the result of the balance of specific interactions with functional groups in protein structure and not specific ones common to all polypeptide chains, and possibly related to amyloid state and to modification of particulates hydration layer.

Towards a rational design of materials for the removal of environmentally relevant cations: polymer inclusion membranes (PIMs) and surface-modified PIMs for Sn2+ sequestration in aqueous solution

This work is focused on the design and preparation of polymer inclusion membranes (PIMs) for potential applications for stannous cation sequestration from water. For this purpose, the membranes have been synthesized employing two polymeric matrices, namely, polyvinylchloride (PVC) and cellulose triacetate (CTA), properly enriched with different plasticizers. The novelty here proposed relies on the modification of the cited PIMs by selected extractants expected to interact with the target cation in the membrane bulk or onto its surface, as well as in the evaluation of their performances in the sequestration of tin(II) in solution through chemometric tools. The composition of both the membrane and the solution for each trial was selected by means of a D-Optimal Experimental Design. The samples such prepared were characterized by means of TG-DTA, DSC, and static contact angles investigations; their mechanical properties were studied in terms of tensile strength and elastic modulus, whereas their morphology was checked by SEM. The sequestering ability of the PIMs toward stannous cation was studied by means of kinetic and isotherm experiments using DP-ASV. The presence of tin in the membranes after the sequestration tests was ascertained by μ-ED-XRF mapping on selected samples.

Evaluation of adsorption ability of cyclodextrin-calixarene nanosponges towards Pb2+ ion in aqueous solution

Different cyclodextrin-calixarene nanosponges (CyCaNSs) have been characterized by means of FFC-NMR relaxometry, and used as sorbents to remove Pb²⁺ ions from aqueous solutions. Considering that the removal treatments may involve polluted waters with different characteristics, the adsorption experiments were performed on solutions without and with the addition of background salts, under different operational conditions. The adsorption abilities and affinities of the nanosponges towards Pb²⁺ ions were investigated by measuring the metal ion concentration by means of Inductively Coupled Plasma Emission Spectroscopy (ICP-OES) and Differential Pulse Anodic Stripping Voltammetry (DP-ASV). The acid-base properties of nanosponges and of metal ion as well as their interactions with the other interacting components of the systems have been considered in the evaluation of adsorption mechanism. Recycling and reuse experiments on the most efficient adsorbents were also performed. On the grounds of the results obtained, post-modified CyCaNSs appear promising materials for designing environmental remediation devices.

Synopsis of Factors Affecting Hydrogen Storage in Biomass-Derived Activated Carbons

Hydrogen (H2) is largely regarded as a potential cost-efficient clean fuel primarily due to its beneficial properties, such as its high energy content and sustainability. With the rising demand for H2 in the past decades and its favorable characteristics as an energy carrier, the escalating USA consumption of pure H2 can be projected to reach 63 million tons by 2050. Despite the tremendous potential of H2 generation and its widespread application, transportation and storage of H2 have remained the major challenges of a sustainable H2 economy. Various efforts have been undertaken by storing H2 in activated carbons, metal organic frameworks (MOFs), covalent organic frameworks (COFs), etc. Recently, the literature has been stressing the need to develop biomass-based activated carbons as an effective H2 storage material, as these are inexpensive adsorbents with tunable chemical, mechanical, and morphological properties. This article reviews the current research trends and perspectives on the role of various properties of biomass-based activated carbons on its H2 uptake capacity. The critical aspects of the governing factors of H2 storage, namely, the surface morphology (specific surface area, pore volume, and pore size distribution), surface functionality (heteroatom and functional groups), physical condition of H2 storage (temperature and pressure), and thermodynamic properties (heat of adsorption and desorption), are discussed. A comprehensive survey of the literature showed that an “ideal” biomass-based activated carbon sorbent with a micropore size typically below 10 Å, micropore volume greater than 1.5 cm3/g, and high surface area of 4000 m2/g or more may help in substantial gravimetric H2 uptake of >10 wt% at cryogenic conditions (−196 °C), as smaller pores benefit by stronger physisorption due to the high heat of adsorption.

Toxic Metal Adsorption from Aqueous Solution by Activated Biochars Produced from Macadamia Nutshell Waste

Abundantly available biomass wastes from agriculture can serve as effective environmental remediation materials. In this study, activated biochar was fabricated from macadamia nutshell (MCN) through carbonization and chemical modification. The resultant biochars were used as adsorbents to remove toxic metal ions such as Cu2+ and Zn2+ from aqueous solutions. The results showed that the activated MCN biochar has a high adsorption capacity for toxic metal ions. When MCN biochar was activated with K2CO3, the adsorption efficiencies for Cu2+ and Zn2+ were 84.02% and 53.42%, respectively. With H3PO4 activation, the Cu2+- and Zn2+-adsorption performances were 95.92% and 67.41%, respectively. H2O2-modified MCN biochar had reasonable Cu2+- and Zn2+-adsorption efficiencies of 79.33% and 64.52%, respectively. The effects of pH, adsorbent concentration and adsorption time on the removal performances of Cu2+ and Zn2+ in aqueous solution were evaluated. The results exhibited that the activated MCN biochar showed quick adsorption ability with an optimal pH of 4 and 4.5 for both Cu2+ and Zn2+, respectively.

A Review of Non-Soil Biochar Applications

Biochar is the solid residue that is recovered after the thermal cracking of biomasses in an oxygen-free atmosphere. Biochar has been used for many years as a soil amendment and in general soil applications. Nonetheless, biochar is far more than a mere soil amendment. In this review, we report all the non-soil applications of biochar including environmental remediation, energy storage, composites, and catalyst production. We provide a general overview of the recent uses of biochar in material science, thus presenting this cheap and waste-derived material as a high value-added and carbonaceous source.