A Review on the Synthesis and Characterization of Biomass-Derived Carbons for Adsorption of Emerging Contaminants from Water

Hydrochars derived from real organic wastes as carbonaceous precursors of activated carbons for the removal of NO from contaminated gas streams

The improvement of air quality in densely-populated urban regions constitutes an environmental challenge of increasing concern. In this respect, the abatement of NO emissions, primarily emanating from combustion processes associated with motor-vehicles, along with industrial/domestic combustion systems, represents one of the main problems. Here, three hydrochars from diverse organic residues were used as activated carbon precursors for their evaluation in the NO removal in two potential application scenarios. Hydrochars were physically activated at 800 °C with pure-CO2 or diluted-O2. These materials were tested in a lab-scale biofilter at different conditions (NO concentration, temperature, relative humidity, NO-containing gas and carbon particle size) and in a larger-scale biofilter to evaluate the long-term NO removal capacity. Hydrochar-derived carbons present a relatively well-developed micro- and mesoporous structure, with BET areas of up to 421 m2/g, and a variety of oxygen surface functionalities (carboxylic, lactone, carbonyl and quinone groups), especially concerning CO2-activated carbons. These exhibited an excellent behaviour at low NO concentration (5 ppmv) between 25 and 75 °C with removal capacities of ≈97 % and > 82 %, respectively; and still good-performance (≈66 %) in a more concentrated gas (120 ppmv). Whilst, carbons obtained by diluted-O2 activation from the same hydrochars, evidenced a higher removal capacity loss at high NO concentration. The O2 presence in the gas stream was confirmed as a crucial factor in the NO elimination, since both co-adsorb on the carbon surface favouring NO oxidation to NO2. Besides, the humidity in the airstream diminished the NO removal capacity from 0.88 to 0.51 mgNO/gcarbon, but still remained at 0.54 mgNO/gcarbon, when the carbon (in pellet) was operated at larger-scale biofilter in 9-fold longer test under humid air. Therefore, this study highlights the potential of renewable carbons to serve as cost-effective component in urban biofilters, to mitigate NO emissions from exhaust gases in biomass boilers and urban semi-close areas.

Valorization of Agriculture Residues into Value-Added Products: A Comprehensive Review of Recent Studies

Global agricultural by-products usually go to waste, especially in developing countries where agricultural products are usually exported as raw products. Such waste streams, once converted to "value-added" products could be an additional source of revenue while simultaneously having positive impacts on the socio-economic well-being of local people. We highlight the utilization of thermochemical techniques to activate and convert agricultural waste streams such as rice and straw husk, coconut fiber, coffee wastes, and okara power wastes commonly found in the world into porous activated carbons and biofuels. Such activated carbons are suitable for various applications in environmental remediation, climate mitigation, energy storage, and conversions such as batteries and supercapacitors, in improving crop productivity and producing useful biofuels.

Investigation of performance of potential adsorbents for emissions mitigation in a diesel generator

Globally, the release of greenhouse gases primarily carbon dioxide (CO2) emissions to our Earth's surface has climbed by  about 45% to its present atmospheric concentration rate of 420 parts per million (ppm) during the industrial era. An unprecedented rise in atmospheric CO2 concentration has been claimed to lead to significant factors such as global warming potential (GWP) and climate change effects.  An increase in atmospheric CO2 concentrations is  a  serious threat to the environment. Recent research efforts have focused on mitigating emissions from anthropogenic point sources. Adsorption-based post-combustion CO2 capture using solid adsorbents is the most effective and efficient method for mitigating gas adsorption in the exhaust system. In the current study, activated carbons are obtained from three potential biomass, namely, (i) coconut shell, (ii) rice husk, and (iii) eucalyptus wood, through a - single-stage activation method. The prepared activated carbon materials are analyzed using proximate and ultimate analyses. Further investigations are performed using different characterization techniques to ensure their adsorption efficiency. Adsorbents are packed one after the other in an in-house fabricated double adsorption chamber and coupled to the exhaust unit of a generator. Test experiments are conducted to examine adsorbents' capture efficiency in emissions mitigation. Adsorbents' adsorption parameters are evaluated in experimental investigations. At 2.5 bar and 50 °C, a maximum loading capacity of samples is achieved by 4.85 mmol/g, 4.58 mmol/g, and 5.96 mmol/g for coconut shell, rice husk, and eucalyptus wood adsorbents, respectively. With a post-combustion carbon adsorption chamber, CO2 and NO are captured about 40-64% and 38-58%, respectively, for all three adsorbents. The thermodynamic parameter of isosteric heat of adsorption value is below 40 kJ/mol, ensuring physisorption for all adsorbents.

DENV-2 Outbreak Associated With Cosmopolitan Genotype Emergence in Western Brazilian Amazon

Background

Dengue virus (DENV) causes an important disease and directly affects public health, being the arbovirus that presents the highest number of infections and deaths in the Western Brazilian Amazon. This virus is divided into 4 serotypes that have already circulated in the region.

Methodology

Molecular characterization of a cohort containing 841 samples collected from febrile patients between 2021 and 2023 was analyzed using a commercial kit to detect the main arboviruses circulating in Brazil: Zika, DENV-1, DENV-2, DENV-3, DENV-4 and, Chikungunya. Subsequently, Sanger sequencing was performed for positive samples.

Results

The cohort detected 162 positive samples, 12 for DENV-1 and 150 identified as DENV-2, indicating co-circulation of serotypes. The samples were subjected to sequencing and the analysis of the sequences that obtained good quality revealed that 5 samples belonged to the V genotype of DENV-1 and 46 were characterized as DENV-2 Cosmopolitan genotype-lineage 5.

Conclusion

The results allowed us to identify for the first time the Cosmopolitan genotype in Rondônia, Brazilian Western Amazon, and its fast spread dispersion.

A review on carbon-based biowaste and organic polymer materials for sustainable treatment of sulfonamides from pharmaceutical wastewater

Frequent detection of sulfonamides (SAs) pharmaceuticals in wastewater has necessitated the discovery of suitable technology for their sustainable remediation. Adsorption has been widely investigated due to its effectiveness, simplicity, and availability of various adsorbent materials from natural and artificial sources. This review highlighted the potentials of carbon-based adsorbents derived from agricultural wastes such as lignocellulose, biochar, activated carbon, carbon nanotubes graphene materials as well as organic polymers such as chitosan, molecularly imprinted polymers, metal, and covalent frameworks for SAs removal from wastewater. The promising features of these materials including higher porosity, rich carbon-content, robustness, good stability as well as ease of modification have been emphasized. Thus, the materials have demonstrated excellent performance towards the SAs removal, attributed to their porous nature that provided sufficient active sites for the adsorption of SAs molecules. The modification of physico-chemical features of the materials have been discussed as efficient means for enhancing their adsorption and reusable performance. The article also proposed various interactive mechanisms for the SAs adsorption. Lastly, the prospects and challenges have been highlighted to expand the knowledge gap on the application of the materials for the sustainable removal of the SAs.

Hierarchical Porous Activated Carbon from Wheat Bran Agro-Waste: Applications in Carbon Dioxide Capture, Dye Removal, Oxygen and Hydrogen Evolution Reactions

This work reports an efficient method for facile synthesis of hierarchically porous carbon (WB-AC) utilizing wheat bran waste. Obtained carbon showed 2.47 mmol g-1 CO2 capture capacity with good CO2 /N2 selectivity and 27.35 to 29.90 kJ mol-1 isosteric heat of adsorption. Rapid removal of MO dye was observed with a capacity of ~555 mg g-1 . Moreover, WB-AC demonstrated a good OER activity with 0.35 V low overpotential at 5 mA cm-2 and a Tafel slope of 115 mV dec-1 . It also exhibited high electrocatalytic HER activity with 57 mV overpotential at 10 mA cm-2 and a Tafel slope of 82.6 mV dec-1 . The large SSA (757 m2  g-1 ) and total pore volume (0.3696 cm3  g-1 ) result from N2 activation contributing to selective CO2 uptake, high and rapid dye removal capacity and superior electrochemical activity (OER/HER), suggesting the use of WB-AC as cost effective adsorbent and metal free electrocatalyst.

Activated carbon prepared from Brazil nut shells towards phenol removal from aqueous solutions

The Brazil nut shell was used as a precursor material for preparing activated carbon by chemical activation with potassium hydroxide. The obtained material (BNSAC) was characterized, and the adsorptive features of phenol were investigated. The characterization showed that the activated carbon presented several rounded cavities along the surface, with a specific surface area of 332 m² g^-1. Concerning phenol adsorption, it was favored using an adsorbent dosage of 0.75 g L^-1 and pH 6. The kinetic investigation revealed that the system approached the equilibrium in around 180 min, and the Elovich model represented the kinetic curves. The Sips model well represented the equilibrium isotherms. In addition, the increase in temperature from 25 to 55 °C favored the phenol adsorption, increasing the maximum adsorption capacity value (q_s) from 83 to 99 mg g^-1. According to the estimated thermodynamic parameters, the adsorption was spontaneous, favorable, endothermic, and governed by physical interactions. Therefore, the Brazil nut shell proved a good precursor material for preparing efficient activated carbon for phenol removal.

A review on arsenic in the environment: bio-accumulation, remediation, and disposal

Arsenic is a widespread serious environmental pollutant as a food chain contaminant and non-threshold carcinogen. Arsenic transfer through the crops-soil-water system and animals is one of the most important pathways of human exposure and a measure of phytoremediation. Exposure occurs primarily from the consumption of contaminated water and foods. Various chemical technologies are utilized for As removal from contaminated water and soil, but they are very costly and difficult for large-scale cleaning of water and soil. In contrast, phytoremediation utilizes green plants to remove As from a contaminated environment. A large number of terrestrial and aquatic weed flora have been identified so far for their hyper metal removal capacity. In the panorama presented herein, the latest state of the art on methods of bioaccumulation, transfer mechanism of As through plants and animals, and remediation that encompass the use of physicochemical and biological processes, i.e., microbes, mosses, lichens, ferns, algae, and macrophytes have been assessed. Since these bioremediation approaches for the clean-up of this contaminant are still at the initial experimental stages, some have not been recognized at full scale. Nonetheless, extensive research on these primitive plants as bio-accumulators can be instrumental in controlling arsenic exposure and rehabilitation and may result in major progress to solve the problem on a worldwide scale.

Sonicating for the Uptake of Paracetamol from Solution by Activated Carbon from Oak: Kinetics, Thermodynamics, and Isotherms

This inquiry used ultrasonic waves to uptake paracetamol (PA) by using oak-based activated carbon (ACO). The surface of ACO was explored based on FT-IR, SEM, and XRD before and after the adsorption. The kinetic data for PA adsorption onto ACO corresponds to a pseudo-second-order kinetic model. Isothermal models of the Langmuir, Freundlich, D-R, and Temkin were used. The adsorption of PA onto ACO was found to be a monolayer with 96.03% uptake, which corresponds to Langmuir. The thermodynamic experiments revealed the endothermic nature of PA adsorption onto ACO. Under the investigated optimal conditions, the adsorption capacity of PA onto ACO was found to be 97.1 mg. L-1. ACO could be recycled after six regenerations. Ultimately, sonicating has adequate performance for the uptake of PA by ACO.

Current research trends on emerging contaminants pharmaceutical and personal care products (PPCPs): A comprehensive review

Pharmaceutical and personnel care products (PPCPs) from wastewater are a potential hazard to the human health and wildlife, and their occurrence in wastewater has caught the concern of researchers recently. To deal with PPCPs, various treatment technologies have been evolved such as physical, biological, and chemical methods. Nevertheless, modern and efficient techniques such as advance oxidation processes (AOPs) demand expensive chemicals and energy, which ultimately leads to a high treatment cost. Therefore, integration of chemical techniques with biological processes has been recently suggested to decrease the expenses. Furthermore, combining ozonation with activated carbon (AC) can significantly enhance the removal efficiency. There are some other emerging technologies of lower operational cost like photo-Fenton method and solar radiation-based methods as well as constructed wetland, which are promising. However, feasibility and practicality in pilot-scale have not been estimated for most of these advanced treatment technologies. In this context, the present review work explores the treatment of emerging PPCPs in wastewater, via available conventional, non-conventional, and integrated technologies. Furthermore, this work focused on the state-of-art technologies via an extensive literature search, highlights the limitations and challenges of the prevailing commercial technologies. Finally, this work provides a brief discussion and offers future research directions on technologies needed for treatment of wastewater containing PPCPs, accompanied by techno-economic feasibility assessment.

Estimation of sulfur fate and contribution to VSC emissions from lakes during algae decay

Algae decay is an important process influencing environmental variables and emissions of volatile sulfur compounds (VSCs) in eutrophic lakes. However, effects of algae decay on VSC emissions from eutrophic lakes as well as fate of algae-derived sulfur remain poorly understood. In this study, simulated algae-sediment systems were used to explore the flow and distribution of sulfur during algae decay. VSCs including hydrogen sulfide (H₂S), methanethiol (CH₃SH), carbon disulfide (CS₂) and dimethyl sulfide ((CH₃)₂S) were detected during algae decay, which increased with algae biomass and eutrophic levels in lakes. During algae decay, the highest H₂S, CH₃SH and (CH₃)₂S emission rates of 10.45, 21.82 and 43.26 μg d^-1 occurred in the first 1-2 days, respectively, while the highest CS₂ emission rates were observed between days 8 and 11. The maximum emissions of H₂S and CS₂ from algae decay were estimated at 0.51 and 0.35 mg m^-2 d^-1 in Lake Taihu, accounting for 1.57% and 0.69% of the total H₂S and CS₂ emissions of in situ, respectively. Algae decay could significantly increase the contents of total sulfur and total carbon in sediments by 2.90%-21.11% and 4.23%-45.05%, respectively. The VSC emissions during algae decay could be predicted using the multiple regression models with the contents of total carbon, total nitrogen and sulfur-containing compounds in sediments. Partial least squares path modelling demonstrated that algae decay had a low direct effect on VSC emissions with a strength of 0.06, while it had a significant influence on environmental variables with a strength of 0.63, which could affect VSC emissions with a strength of 0.85, indicating VSC emissions from eutrophic lakes were affected by the environmental variables rather than the direct influence of algae decay. These findings illustrated the mechanisms of VSC emissions during algae decay and provided insights into VSC control and mitigation for eutrophic lakes.

Adsorption of vanadium (V) ions from the aqueous solutions on different biomass-derived biochars

The paper presents the results of the studies on the vanadium (V) ions removal from the aqueous solutions in the adsorption process on biochars from different biomass types (cow manure BC1, wet distiller grains BC2, spent mushroom substrates BC3). The adsorbents were characterized by means of the SEM-EDS, FTIR, XRD and XPS techniques. The influence of adsorbent type and basic process parameters, such as pH and metal ion concentration in aqueous phase, adsorbent dose and time of contact of phases on the efficiency of V(V) was determined. Based on the obtained results, the mechanism and kinetics of the adsorption processes occurring on the biochar originating from the wet distiller grains as adsorbents with the greatest affinity for the V(V) ions were characterized, using isotherm models of Langmuir, Freundlich, Temkin and Dubinin-Radushkevich and pseudo-first-order, pseudo-second-order as well as intraparticle diffusion kinetic models. Under the constant process conditions (pH = 3.0; m = 0.5 g; c₀ = 50 mg/L) the order of V(V) ions removal from aqueous solutions was as follows: BC2 > BC1 = BC3. The biochar BC2 exhibited the maximum sorption capacity of 1.61 mg V(V)/g. The experimental kinetic data show the adsorption course according to the pseudo-second order model.

Carbon-Based Nanocatalysts (CnCs) for Biomass Valorization and Hazardous Organics Remediation

The continuous increase of the demand in merchandise and fuels augments the need of modern approaches for the mass-production of renewable chemicals derived from abundant feedstocks, like biomass, as well as for the water and soil remediation pollution resulting from the anthropogenic discharge of organic compounds. Towards these directions and within the concept of circular (bio)economy, the development of efficient and sustainable catalytic processes is of paramount importance. Within this context, the design of novel catalysts play a key role, with carbon-based nanocatalysts (CnCs) representing one of the most promising class of materials. In this review, a wide range of CnCs utilized for biomass valorization towards valuable chemicals production, and for environmental remediation applications are summarized and discussed. Emphasis is given in particular on the catalytic production of 5-hydroxymethylfurfural (5-HMF) from cellulose or starch-rich food waste, the hydrogenolysis of lignin towards high bio-oil yields enriched predominately in alkyl and oxygenated phenolic monomers, the photocatalytic, sonocatalytic or sonophotocatalytic selective partial oxidation of 5-HMF to 2,5-diformylfuran (DFF) and the decomposition of organic pollutants in aqueous matrixes. The carbonaceous materials were utilized as stand-alone catalysts or as supports of (nano)metals are various types of activated micro/mesoporous carbons, graphene/graphite and the chemically modified counterparts like graphite oxide and reduced graphite oxide, carbon nanotubes, carbon quantum dots, graphitic carbon nitride, and fullerenes.

Chemical Modification of Teff Straw Biomass for Adsorptive Removal of Cr (VI) from Aqueous Solution: Characterization, Optimization, Kinetics, and Thermodynamic Aspects

Teff straw, a by-product of Teff, mainly available in Ethiopia, has not been studied much for biosorbent production. The present study has investigated the effects of modification and optimization of process parameters (viz., concentration of modifying agent (H3PO4 and KOH), modifying temperature, and modifying time) on the Cr (VI) removal efficiency of using chemically activated Teff straw biosorbent by RSM followed by BBD. The maximum Cr (VI) removal was obtained using an H3PO4-modified Teff straw biosorbent of 92.5% with 2 M concentration of the modifying agent, 110°C, and 4 h. Similarly, maximum Cr (VI) removal using KOH-modified Teff straw biosorbent of 95.2% was obtained with 1.5 M activating agent concentration, 105°C activation temperature, and 3.5 h activation time. In addition, the effects of adsorption parameters (viz., biosorbent dosage, temperature, initial concentration of Cr (VI), and contact time) were investigated. The maximum removal efficiency was attained at 2 g of biosorbent dosage, 4 h contact, 75 mg/L of initial Cr (VI) concentration, and 25°C sorption temperature. In addition, isotherm, kinetic, and thermodynamic studies for Cr (VI) biosorption were studied. The experimental adsorption data were well fitted with the Langmuir isotherm and pseudo-second-order kinetic model with higher correlation coefficient in both untreated and chemically modified Teff straw biosorbent. The investigated thermodynamic parameters ( $\Delta H^o$ , $\Delta S^o$ , and $\Delta G^o$ ) confirmed that Cr (VI) metal ions’ adsorption process onto Teff straw biosorbent was spontaneous and endothermic.

The Adsorption of Copper, Lead Metal Ions, and Methylene Blue Dye from Aqueous Solution by Pure and Treated Fennel Seeds

This research work reports on pure and acid-treated fennel seed biomaterials for the removal of metal ions of copper Cu(II), lead Pb(II), and methylene blue (MB) dye from aqueous solution by batch adsorption. Pure fennel seeds were labelled as PFS; nitric and sulphuric acid-treated seeds were designated as NAFS and SAFS, respectively. The adsorbents were characterised by SEM, EDX, FTIR, XRD, and BET. The SEM images revealed that the surface of the adsorbents was porous. However, physicochemical characterization further revealed that BET surface area, pore size, and pore width increased for NAFS and SAFS compared to PFS. FTIR results revealed that the peaks for cellulose −COC and −OH decreased considerably for NAFS and SAFS; this indicated that cellulose was hydrolyzed during acid treatment. Adsorption data showed that all biomaterials had a higher affinity for MB dye more than Pb(II) and Cu(II) metal ions. The maximum adsorption capacities onto PFS were 6.834, 4.179, and 2.902 mg/g and onto NAFS are 15.28, 14.44, and 4.475 mg/g, while those onto SAFS are 19.81, 18.79 and 6.707 mg/g respective for MB dye, Pb(II), and Cu(II) ions. Postadsorption analysis revealed that adsorption of Pb(II) and Cu(II) was controlled mainly by the electrostatic attraction, while that of MB was synergistic of electrostatic attraction, π-π interaction, and hydrogen bond. It was found that the uptake processes of MB dye onto all adsorbents fitted Freundlich while both cations were described by Langmuir model. The thermodynamic parameters $\Delta H$ o and $\Delta G$ o indicated the endothermic nature and spontaneity of the processes, respectively.

Transport of Carbamazepine, Ciprofloxacin and Sulfamethoxazole in Activated Carbon: Solubility and Relationships between Structure and Diffusional Parameters

The transport of carbamazepine, ciprofloxacin and sulfamethoxazole in the different pores of activated carbon in an aqueous solution is a dynamic process that is entirely dependent on the intrinsic parameters of these molecules and of the adsorbent. The macroscopic processes that take place are analyzed by interfacial diffusion and reaction models. Modeling of the experimental kinetic curves obtained following batch treatment of each solute at 2 µg/L in tap water showed (i) that the transport and sorption rates were controlled by external diffusion and intraparticle diffusion and (ii) that the effective diffusion coefficient for each solute, with the surface and pore diffusion coefficients, were linked by a linear relationship. A statistical analysis of the experimental data established correlations between the diffusional parameters and some geometrical parameters of these three molecules. Given the major discontinuities observed in the adsorption kinetics, the modeling of the experimental data required the use of traditional kinetic models, as well as a new kinetic model composed of the pseudo first or second order model and a sigmoidal expression. The predictions of this model were excellent. The solubility of each molecule below 60 °C was formulated by an empirical expression.

Applications of chitin and chitosan based biomaterials for the adsorptive removal of textile dyes from water - A comprehensive review

The presence of pollutants in the water bodies deteriorate the water quality and make it unfit for use. From an environmental perspective, it is essential to develop new technologies for the wastewater treatment and recycling of dye contaminated water. The surface modified chitin and chitosan biopolymeric composites based adsorbents, have an important role in the toxic organic dyes from removal wastewater. The surface modification of biopolymers with various organics and inorganics produces more active sites at the surface of the adsorbent, which enhances dye and adsorbent interaction more reliable. Herein, the work brought in the thought of the application of various chitin and chitosan composites in wastewater remediation and suggested the versatility in composites for the development of rapid, selective and effective removal processes for the detoxification of a variety of organic dyes. It further emphasizes the existing obstruction and impending prediction for the deprivation of dyes via adsorption techniques.

Sustainable materials in the removal of pesticides from contaminated water: Perspective on macro to nanoscale cellulose

Recently, over utilization of pesticides in agrarian and non- agrarian sectors has resulted in a significant increment in the deposition of their remnants in different segments of the environmental media. The presence of pesticides and transportation of their different metabolites in rivers, ponds, lakes, soils, air, groundwater sources and drinkable water sources has demonstrated a high threat to human wellbeing and the climate. Thus, the removal of pesticides and their metabolites from contaminated water is imperative to lessen the ill effects of pesticides on human beings. In the present article, we have appraised recent advances in pesticides removal utilizing low cost pristine and functionalized cellulose biomass-based derivatives. One of the key focus has been on better understand the destiny of pesticides in the environment as well as their behaviour in the water. In addition, the impact of magnetite cellulose nanocomposites, cellulose derived photo nano-catalyst, cellulose/clay nano composites, CdS/cellulose nanocomposites and activated carbons/biochar on percent removal of pesticides have also been a part of the current review. The impact of different parameters such as adsorbent dosage, pH, time of contact and initials pesticide concentration on adsorption capacity and adsorption kinetics followed during absorption by different cellulosic bio-adsorbents has also been given. The cellulosic biomass is highly efficient in the removal of pesticides and their efficiency further increases upon functionalization or their conversion into activated carbons forms. Nano particles loaded cellulosic materials have in general found to be less efficient than raw, functionalized cellulosic materials and activated carbons. Further, among different nano particles loaded with cellulose-based materials, cellulose/MnO₂ photonanocatalyst were noticed to be more effective. So considerable efforts should be given to determine the finest practices that relate to the dissipation of different pesticides from the water.

Support-Activity Relationship in Heterogeneous Catalysis for Biomass Valorization and Fine-Chemicals Production

Heterogeneous catalysts are progressively expanding their field of application, from high-throughput reactions for traditional industrial chemistry with production volumes reaching millions of tons per year, a sector in which they are key players, to more niche applications for the production of fine chemicals. These novel applications require a progressive utilization reduction of fossil feedstocks, in favor of renewable ones. Biomasses are the most accessible source of organic precursors, having as advantage their low cost and even distribution across the globe. Unfortunately, they are intrinsically inhomogeneous in nature and their efficient exploitation requires novel catalysts. In this process, an accurate design of the active phase performing the reaction is important; nevertheless, we are often neglecting the importance of the support in guaranteeing stable performances and improving catalytic activity. This review has the goal of gathering and highlighting the cases in which the supports (either derived or not from biomass wastes) share the worth of performing the catalysis with the active phase, for those reactions involving the synthesis of fine chemicals starting from biomasses as feedstocks.

Recent developments in physical, biological, chemical, and hybrid treatment techniques for removing emerging contaminants from wastewater

Emerging contaminants (ECs) in wastewater have recently attracted the attention of researchers as they pose significant risks to human health and wildlife. This paper presents the state-of-art technologies used to remove ECs from wastewater through a comprehensive review. It also highlights the challenges faced by existing EC removal technologies in wastewater treatment plants and provides future research directions. Many treatment technologies like biological, chemical, and physical approaches have been advanced for removing various ECs. However, currently, no individual technology can effectively remove ECs, whereas hybrid systems have often been found to be more efficient. A hybrid technique of ozonation accompanied by activated carbon was found significantly effective in removing some ECs, particularly pharmaceuticals and pesticides. Despite the lack of extensive research, nanotechnology may be a promising approach as nanomaterial incorporated technologies have shown potential in removing different contaminants from wastewater. Nevertheless, most existing technologies are highly energy and resource-intensive as well as costly to maintain and operate. Besides, most proposed advanced treatment technologies are yet to be evaluated for large-scale practicality. Complemented with techno-economic feasibility studies of the treatment techniques, comprehensive research and development are therefore necessary to achieve a full and effective removal of ECs by wastewater treatment plants.

Adsorption of ciprofloxacin from aqueous solution using surface improved tamarind shell as an economical and effective adsorbent

Antibiotics in water bodies are emerging as an alarming new pollutant because of its persistent and recombinant nature. In recent period of human lifestyle, pharmaceutical products play a vital role in many perspectives. Due to this unpredictable usage of products, the unreacted components release into waterbodies in trace quantities. Eventhough these trace quantities initiate a crisis of developing resistant antibacterial strains which pose health risks to humans and animals. This work reports the batch adsorption of a fluoroquinolone, a fourth-generation antibiotic compound by a biosorbent made by acid-treated tamarind shells. The shells were treated with zinc chloride and hydrochloric acid. The characterization of biosorbent was performed by Fourier transform infrared spectroscopy and field emission scanning electron microscopy. The optimized adsorption parameters of time, pH and temperature were 30 minutes, 6 and 60 °C. The adsorbent can be reused up to seven times with negligible loss in its adsorption capacity. Adsorption followed by Langmuir, Freundlich and Tempkin model where used to determine the correlation coefficient. Pseudo first-order, second-order and intra-particle kinetic model were used to fit the experimental data. The results are best described by pseudo second-order denoting chemisorption and Freundlich isotherm model describing multilayer adsorption.Novelty StatementThe proposed work is to investigate about improved tamarind shell as biomass used in the removal unreacted PPCP components that have been released into aquatic environment.The novelty of this paper lies in that it puts forward a better resource utilization method for treating PPCP component wastewater, and studies the method theoretically from the perspective of mechanism and proves its feasibility.Identifying the maximum adsorption of antibiotic component from wastewater under different conditions and finding the optimum range.In addition to the existing literatures, this study has compared the adsorption efficiency of raw and treated adsorbent material prepared using Tamarind shell.

Activated Olive Stones as a Low-Cost and Environmentally Friendly Adsorbent for Removing Cephalosporin C from Aqueous Solutions

In this paper, we describe the removal of cephalosporin C (CPC) from aqueous solutions by adsorption onto activated olive stones (AOS) in a stirred tank. For comparative purposes, several experiments of adsorption onto commercial granular activated carbon were carried out. A quantum study of the different species of cephalosporin C that, depending on the pH, exist in aqueous solution pointed to a favorable mass transfer process during adsorption. Activated olive stones were characterized by SEM, EDX and IR techniques and their pHzc was determined. A 10-3 M HCl cephalosporin C solution has been selected for the adsorption experiments because at the pH of that solution both electrostatic and hydrogen bond interactions are expected to be established between the adsorbate and the adsorbent. The adsorption process is best described by the Freundlich isotherm model and the pseudo-second-order kinetic model, while the adsorption mechanism is mainly controlled by film diffusion. Under the conditions studied, the adsorption process is of a physical nature, endothermic and spontaneous. Comparison of the adsorption results obtained in this paper with those of other authors shows that the efficiency of AOS is 20% of that of activated carbon but 65% higher than that of the XAD-2 adsorbent. Considering its low price, abundance, easy accessibility and eco-compatibility, the use of activated olive stones as adsorbents for the removal of emerging pollutants from aqueous solutions represents an interesting possibility from both the economic and the environmental points of view.

Process optimization with acid functionalised activated carbon derived from corncob for production of 4-hydroxymethyl-2,2-dimethyl-1,3-dioxolane and 5-hydroxy-2,2-dimethyl-1,3-dioxane

In this article, a two-step activated carbon preparation technique from corncob has been elucidated. The derived catalysts AAC-CC has been characterized using various techniques for the determination of their structural properties and compared with AC-CC, already reported with another article. The conjugated boat structure of AAC-CC resulted in a very high surface area (779.8 m2/g) and high pore volume (0.428 cc/g). This unveils the suitability of AAC-CC as better among the two catalytic pathways for solketal production. The activated carbons so prepared have been used for the valorization of glycerol to produce 2,2-Dimethyl-1,3-dioxolane-4-methanol (solketal), oxygenated additives to fuel. The face-centered composite design (FCCD) of RSM was applied for the optimization of the reaction parameters for the ketalisation reaction using AAC-CC as a catalyst. From the optimized results, the acidic catalyst AAC-CC resulted in a glycerol conversion, i.e. 80.3% under the actual laboratory experiment. Moreover, the catalyst could be reused for three consecutive batch reactions without (< 5%) much reduction of activity and no distinctive structural deformity.

One novel composite based on functionalized magnetic peanut husk as adsorbent for efficient sequestration of phosphate and Congo red from solution: Characterization, equilibrium, kinetic and mechanism studies

Accessibility to quality and clean water has in recent times been compromised due to the presence of pollutants, thus posing as a threat to the survival of living organisms. The adsorption technique in this regard has been observed to be useful in the remediation process with the material used as the adsorbent playing an integral role. In this study, a novel biocomposite (PN-Fe₃O₄-IDA-Al) based on peanut husk (a low-cost material) was developed by functionalization with aluminum (Al), iminodiacetic acid (IDA) and Fe₃O₄. The efficiency of PN-Fe₃O₄-IDA-Al as an adsorbent for the remediation of wastewater was evaluated using Congo red (CR) and phosphates (PO₄^3-) as model pollutants. The results from the characterization studies confirmed PN-Fe₃O₄-IDA-Al to have superparamagnetic properties which ensures its easy retrieval. Adsorption studies indicated that PN-Fe₃O₄-IDA-Al had a maximum monolayer capacity of 79.0 ± 2.0 and 16.8 ± 2.5 mg g^-1 for CR and PO₄^3- (according to P), respectively, which was significantly dependent on factors such as reaction time, solution pH, temperature and the presence of some common anions. The Freundlich model was observed to better describe both adsorption processes with chemisorption being the principal underlying mechanism. Results from using real water samples confirmed PN-Fe₃O₄-IDA-Al to be highly efficient for practical remediation processes. These results coupled with the synthesis of PN-Fe₃O₄-IDA-Al under benign conditions using low-cost materials help to expound the knowledge on the use of low cost materials as the basis for the development of highly efficient adsorbents for wastewater remediation.

Biochars as media for air pollution control systems: Contaminant removal, applications and future research directions

Biochars are low-cost and renewable biomaterials with several applications, including soil amendment, mitigation of greenhouse gas emissions, and removal of both inorganic and organic contaminants in aqueous systems. An increasing body of recent evidence indicates that biochars can also remove gaseous chemical contaminants, such as those occurring in industrial flue gases. However, unlike other applications such as in agroecosystems, soil amendments, and aquatic systems, comprehensive reviews on biochar applications in the field of air pollution control are still lacking. The current paper examined existing evidence to understand the nature of contaminants, particularly the gaseous ones, potential applications, constraints, and future research needs pertaining to biochar applications in air pollution control. The preparation of biochars and their functionalized derivatives, and the properties influencing their capacity to remove gaseous contaminants are summarized. The removal capacity and mechanisms of various organic and inorganic gaseous contaminants by biochars are discussed. Evidence shows that biochars effectively remove metal vapours, particularly elemental mercury (Hg⁰), acidic gases (H₂S, SO₂, CO₂), ozone, nitrogen oxides (NO_x), and organic contaminants including aromatic compounds, volatile organic compounds, and odorous substances. The mechanisms for the removal of gaseous contaminants, including; adsorption, precipitation, and size exclusion were presented. Potential industrial application domains include remediation of gaseous emissions from incinerators, waste-to-energy systems, kilns, biomass and coal-fired boilers/cookers, cremation, smelters, wastewater treatment, and agricultural production systems including livestock husbandry. These industrial applications, coupled with the renewable, low-cost and sustainable nature of biochars, point to opportunities to further develop and scale up the biochar technology in the air pollution control industry. However, the biochar-based air filter technology still faces several challenges, largely stemming from constraints and several knowledge gaps, which were highlighted. Hence, further research is required to address these constraints and knowledge gaps before the benefits of the biochar-based air filters are realized.

A Critical Review on Metal-Organic Frameworks and Their Composites as Advanced Materials for Adsorption and Photocatalytic Degradation of Emerging Organic Pollutants from Wastewater

Water-borne emerging pollutants are among the greatest concern of our modern society. Many of these pollutants are categorized as endocrine disruptors due to their environmental toxicities. They are harmful to humans, aquatic animals, and plants, to the larger extent, destroying the ecosystem. Thus, effective environmental remediations of these pollutants became necessary. Among the various remediation techniques, adsorption and photocatalytic degradation have been single out as the most promising. This review is devoted to the compilations and analysis of the role of metal-organic frameworks (MOFs) and their composites as potential materials for such applications. Emerging organic pollutants, like dyes, herbicides, pesticides, pharmaceutical products, phenols, polycyclic aromatic hydrocarbons, and perfluorinated alkyl substances, have been extensively studied. Important parameters that affect these processes, such as surface area, bandgap, percentage removal, equilibrium time, adsorption capacity, and recyclability, are documented. Finally, we paint the current scenario and challenges that need to be addressed for MOFs and their composites to be exploited for commercial applications.

An Overview and Evaluation of Highly Porous Adsorbent Materials for Polycyclic Aromatic Hydrocarbons and Phenols Removal from Wastewater

Polycyclic aromatic hydrocarbons (PAHs) and phenolic compounds had been widely recognized as priority organic pollutants in wastewater with toxic effects on both plants and animals. Thus, the remediation of these pollutants has been an active area of research in the field of environmental science and engineering. This review highlighted the advantage of adsorption technology in the removal of PAHs and phenols in wastewater. The literature presented on the applications of various porous carbon materials such as biochar, activated carbon (AC), carbon nanotubes (CNTs), and graphene as potential adsorbents for these pollutants has been critically reviewed and analyzed. Under similar conditions, the use of porous polymers such as Chitosan and molecularly imprinted polymers (MIPs) have been well presented. The high adsorption capacities of advanced porous materials such as mesoporous silica and metal-organic frameworks have been considered and evaluated. The preference of these materials, higher adsorption efficiencies, mechanism of adsorptions, and possible challenges have been discussed. Recommendations have been proposed for commercialization, pilot, and industrial-scale applications of the studied adsorbents towards persistent organic pollutants (POPs) removal from wastewater.

Biochar and Energy Production: Valorizing Swine Manure through Coupling Co-Digestion and Pyrolysis

Anaerobic digestion is an established technological option for the treatment of agricultural residues and livestock wastes beneficially producing renewable energy and digestate as biofertilizer. This technology also has significant potential for becoming an essential component of biorefineries for valorizing lignocellulosic biomass due to its great versatility in assimilating a wide spectrum of carbonaceous materials. The integration of anaerobic digestion and pyrolysis of its digestates for enhanced waste treatment was studied. A theoretical analysis was performed for three scenarios based on the thermal needs of the process: The treatment of swine manure (scenario 1), co-digestion with crop wastes (scenario 2), and addition of residual glycerine (scenario 3). The selected plant design basis was to produce biochar and electricity via combined heat and power units. For electricity production, the best performing scenario was scenario 3 (producing three times more electricity than scenario 1), with scenario 2 resulting in the highest production of biochar (double the biochar production and 1.7 times more electricity than scenario 1), but being highly penalized by the great thermal demand associated with digestate dewatering. Sensitivity analysis was performed using a central composite design, predominantly to evaluate the bio-oil yield and its high heating value, as well as digestate dewatering. Results demonstrated the effect of these parameters on electricity production and on the global thermal demand of the plant. The main significant factor was the solid content attained in the dewatering process, which excessively penalized the global process for values lower than 25% TS.

Review on Activated Carbons by Chemical Activation with FeCl3

This study reviews the most relevant results on the synthesis, characterization, and applications of activated carbons obtained by novel chemical activation with FeCl3. The text includes a description of the activation mechanism, which compromises three different stages: (1) intense de-polymerization of the carbon precursor (up to 300 °C), (2) devolatilization and formation of the inner porosity (between 300 and 700 °C), and (3) dehydrogenation of the fixed carbon structure (>700 °C). Among the different synthesis conditions, the activation temperature, and, to a lesser extent, the impregnation ratio (i.e., mass ratio of FeCl3 to carbon precursor), are the most relevant parameters controlling the final properties of the resulting activated carbons. The characteristics of the carbons in terms of porosity, surface chemistry, and magnetic properties are analyzed in detail. These carbons showed a well-developed porous texture mainly in the micropore size range, an acidic surface with an abundance of oxygen surface groups, and a superparamagnetic character due to the presence of well-distributed iron species. These properties convert these carbons into promising candidates for different applications. They are widely analyzed as adsorbents in aqueous phase applications due to their porosity, surface acidity, and ease of separation. The presence of stable and well-distributed iron species on the carbons’ surface makes them promising catalysts for different applications. Finally, the presence of iron compounds has been shown to improve the graphitization degree and conductivity of the carbons; these are consequently being analyzed in energy storage applications.

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.

Characterizing the Suitability of Granular Fe0 for the Water Treatment Industry

There is a burgeoning interest in reliably characterizing the intrinsic reactivity of metallic iron materials (Fe0) or zero-valent iron materials (ZVI) used in the water treatment industry. The present work is a contribution to a science-based selection of Fe0 for water treatment. A total of eight (8) granular ZVI materials (ZVI1 to ZVI8) were tested. Fe0 dissolution in ethylenediaminetetraacetic acid (EDTA test) and 1,10-Phenanthroline (Phen test) is characterized in parallel experiments for up to 250 h (10 days). 50 mL of each solution and 0.1 g of each Fe0 material are equilibrated in quiescent batch experiments using 2 mM EDTA or Phen. Results indicated a far higher extent of iron dissolution in EDTA than in Phen under the experimental conditions. The tested materials could be grouped into three reactivity classes: (i) low (ZVI4, ZVI6, ZVI7, and ZVI8), (ii) moderate (ZVI1 and ZVI5) and (iii) high (ZVI2 and ZVI3). The order of reactivity was the same for both tests: ZVI2 ≅ ZVI3 > ZVI1 ≅ ZVI5 > ZVI4 ≅ ZVI6 ≅ ZVI7 ≅ ZVI8. Phen results revealed for the first time the time-dependent variation of the kinetics of iron corrosion (corrosion rate) in short-term batch experiments. Overall, the results demonstrated the superiority of the Phen test for evaluating the initial stage of Fe0 dissolution. Long-term column experiments are recommended to deepen the acquired knowledge.

Biochar as a Multifunctional Component of the Environment—A Review

The growing demand for electricity, caused by dynamic economic growth, leads to a decrease in the available non-renewable energy resources constituting the foundation of global power generation. A search for alternative sources of energy that can support conventional energy technologies utilizing fossil fuels is not only of key significance for the power industry but is also important from the point of view of environmental conservation and sustainable development. Plant biomass, with its specific chemical structure and high calorific value, is a promising renewable source of energy which can be utilized in numerous conversion processes, enabling the production of solid, liquid, and gaseous fuels. Methods of thermal biomass conversion include pyrolysis, i.e., a process allowing one to obtain a multifunctional product known as biochar. The article presents a review of information related to the broad uses of carbonization products. It also discusses the legal aspects and quality standards applicable to these materials. The paper draws attention to the lack of uniform legal and quality conditions, which would allow for a much better use of biochar. The review also aims to highlight the high potential for a use of biochar in different environments. The presented text attempts to emphasize the importance of biochar as an alternative to classic products used for energy, environmental and agricultural purposes.

Effect of Activating Agent on the Properties of TiO₂/Activated Carbon Heterostructures for Solar Photocatalytic Degradation of Acetaminophen

Several activated carbons (ACs) were prepared by chemical activation of lignin with different activating agents (FeCl₃, ZnCl₂, H₃PO₄ and KOH) and used for synthesizing TiO₂/activated carbon heterostructures. These heterostructures were obtained by the combination of the activated carbons with a titania precursor using a solvothermal treatment. The synthesized materials were fully characterized (Wavelength-dispersive X-ray fluorescence (WDXRF), X-ray diffraction (XRD), Scanning electron microscopy (SEM), N2 adsorption-desorption, Fourier transform infrared (FTIR) and UV-visible diffuse reflectance spectra (UV-Vis DRS) and further used in the photodegradation of a target pharmaceutical compound (acetaminophen). All heterostructures were composed of anatase phase regardless of the activated carbon used, while the porous texture and surface chemistry depended on the chemical compound used to activate the lignin. Among all heterostructures studied, that obtained by FeCl₃-activation yielded complete conversion of acetaminophen after 6 h of reaction under solar-simulated irradiation, also showing high conversion after successive cycles. Although the reaction rate was lower than the observed with bare TiO₂, the heterostructure showed higher settling velocity, thus being considerably easier to recover from the reaction medium.