Cross-linked FeCl3-activated seaweed carbon/MCM-41/alginate hydrogel composite for effective biosorption of bisphenol A plasticizer and basic dye from aqueous solution

Seafood waste derived carbon nanomaterials for removal and detection of food safety hazards

Nanobiotechnology and the engineering of nanomaterials are currently the main focus of many researches. Seafood waste carbon nanomaterials (SWCNs) are a renewable resource with large surface area, porous structure, high reactivity, and abundant active sites. They efficiently adsorb food contaminants through π-π conjugated, ion exchange, and electrostatic interaction. Furthermore, SWCNs prepared from seafood waste are rich in N and O functional groups. They have high quantum yield (QY) and excellent fluorescence properties, making them promising materials for the removal and detection of pollutants. It provides an opportunity by which solutions to the long-term challenges of the food industry in assessing food safety, maintaining food quality, detecting contaminants and pretreating samples can be found. In addition, carbon nanomaterials can be used as adsorbents to reduce environmental pollutants and prevent food safety problems from the source. In this paper, the types of SWCNs are reviewed; the synthesis, properties and applications of SWCNs are reviewed and the raw material selection, preparation methods, reaction conditions and formation mechanisms of biomass-based carbon materials are studied in depth. Finally, the advantages of seafood waste carbon and its composite materials in pollutant removal and detection were discussed, and existing problems were pointed out, which provided ideas for the future development and research directions of this interesting and versatile material. Based on the concept of waste pricing and a recycling economy, the aim of this paper is to outline current trends and the future potential to transform residues from the seafood waste sector into valuable biological (nano) materials, and to apply them to food safety.

Preparation of Activated Carbon-Reinforced Composite Beads Based on MnO2/MCM-41@Fe3O4 and Calcium Alginate for Efficient Removal of Tetracycline in Aqueous Solutions

Tetracycline (TC) is a common antibiotic; when untreated TC enters the environment, it will cause a negative impact on the human body through the food chain. In the present study, MnO2/MCM-41@Fe3O4 (FeMnMCM) prepared using a hydrothermal and redox method and Camellia oleifera shell-activated carbon (COFAC) prepared through alkali activation were encapsulated using alginate (ALG) and calcium chloride as a cross-linking matrix to give the composite beads COFAC-FeMnMCM-ALG. The resultant COFAC-FeMnMCM-ALG composite beads were then carefully characterized, showing a high immobilization of MnO2/MCM-41@Fe3O4, with porous COFAC as an effective bioadsorbent for enriching the pollutants in the treated samples. These bead catalysts were subsequently applied to the oxidative degradation of TC in a Fenton oxidation system. Several parameters affecting the degradation were investigated, including the H2O2 concentration, catalyst dosage, initial TC concentration, and temperature. A very high catalytic activity towards the degradation of TC was demonstrated. The electron paramagnetic resonance (EPR) and quenching results showed that ·OH and ·O2- were generated in the system, with ·OH as the main radical species. In addition, the COFAC-FeMnMCM-ALG catalyst exhibited excellent recyclability/reusability. We conclude that the as-prepared COFAC-FeMnMCM-ALG composite beads, which integrate MnO2 and Fe3O4 with bioadsorbents, provide a new idea for the design of catalysts for advanced oxidation processes (AOPs) and have great potential in the Fenton oxidation system to degrade toxic pollutants.

Emerging environmentally friendly bio-based nanocomposites for the efficient removal of dyes and micropollutants from wastewater by adsorption: a comprehensive review

Water scarcity will worsen due to population growth, urbanization, and climate change. Addressing this issue requires developing energy-efficient and cost-effective water purification technologies. One approach is to use biomass to make bio-based materials (BBMs) with valuable attributes. This aligns with the goal of environmental conservation and waste management. Furthermore, the use of biomass is advantageous because it is readily available, economical, and has minimal secondary environmental impact. Biomass materials are ideal for water purification because they are abundant and contain important functional groups like hydroxyl, carboxyl, and amino groups. Functional groups are important for modifying and absorbing contaminants in water. Single-sourced biomass has limitations such as weak mechanical strength, limited adsorption capacity, and chemical instability. Investing in research and development is crucial for the development of efficient methods to produce BBMs and establish suitable water purification application models. This review covers BBM production, modification, functionalization, and their applications in wastewater treatment. These applications include oil-water separation, membrane filtration, micropollutant removal, and organic pollutant elimination. This review explores the production processes and properties of BBMs from biopolymers, highlighting their potential for water treatment applications. Furthermore, this review discusses the future prospects and challenges of developing BBMs for water treatment and usage. Finally, this review highlights the importance of BBMs in solving water purification challenges and encourages innovative solutions in this field.

Biochar assisted cultivation of Chlorella protothecoides for adsorption of tetracycline and electrochemical study on self-cultured Chlorella protothecoides

Microalgae present a viable mechanism for purifying aquatic environments through the absorption of organic pollutants. In this paper, Chlorella protothecoides was cultured in a tetracycline environment, and biochar was added during the cultivation process. Compared with conventionally cultured Chlorella protothecoides, the addition of biochar for cultivation under a tetracycline environment increased the biomass of Chlorella protothecoides by 13.26 %. Moreover, the adsorption of tetracycline by biochar alone was not complete, but when mixed with Chlorella protothecoides, tetracycline was completely removed, which proved the biosorption of Chlorella protothecoides for low concentrations of tetracycline. Finally, the cultured Chlorella protothecoides was used further to prepare electrode materials, and it was found that the specific capacitance of the material reached 233.15F/g at a current density of 1 A/g. In this study, the use of biochar and Chlorella protothecoides to jointly adsorb tetracycline is of great significance for environmental protection and microalgae cultivation.

Bisphenol A contamination in aquatic environments: a review of sources, environmental concerns, and microbial remediation

The production of polycarbonate, a high-performance transparent plastic, employs bisphenol A, which is a prominent endocrine-disrupting compound. Polycarbonates are frequently used in the manufacturing of food, bottles, storage containers for newborns, and beverage packaging materials. Global production of BPA in 2022 was estimated to be in the region of 10 million tonnes. About 65-70% of all bisphenol A is used to make polycarbonate plastics. Bisphenol A leaches from improperly disposed plastic items and enters the environment through wastewater from plastic-producing industries, contaminating, sediments, surface water, and ground water. The concentration BPA in industrial and domestic wastewater ranges from 16 to 1465 ng/L while in surface water it has been detected 170-3113 ng/L. Wastewater treatment can be highly effective at removing BPA, giving reductions of 91-98%. Regardless, the remaining 2-9% of BPA will continue through to the environment, with low levels of BPA commonly observed in surface water and sediment in the USA and Europe. The health effects of BPA have been the subject of prolonged public and scientific debate, with PubMed listing more than 17,000 scientific papers as of 2023. Bisphenol A poses environmental and health hazards in aquatic systems, affecting ecosystems and human health. While several studies have revealed its presence in aqueous streams, environmentally sound technologies should be explored for its removal from the contaminated environment. Concern is mostly related to its estrogen-like activity, although it can interact with other receptor systems as an endocrine-disrupting chemical. Present review article encompasses the updated information on sources, environmental concerns, and sustainable remediation techniques for bisphenol A removal from aquatic ecosystems, discussing gaps, constraints, and future research requirements.

Effective Removal of Dyes from Wastewater by Osmanthus Fragrans Biomass Charcoal

The exploration of low-cost, high-performance adsorbents is a popular research issue. In this work, a straightforward method that combined hydrothermal with tube firing was used to produce Osmanthus fragrans biomass charcoal (OBC) from low-cost osmanthus for dye adsorption in water. The study examined the parameters of starting concentration, pH, and duration, which impacted the process of adsorption of different dyes by OBC. The analysis showed that the adsorption capacities of OBC for six dyes: malachite green (MG, C0 = 800 mg/L, pH = 7), Congo red (CR, C0 = 1000 mg/L, pH = 8), rhodamine B (RhB, C0 = 500 mg/L, pH = 6), methyl orange (MO, C0 = 1000 mg/L, pH = 7), methylene blue (MB, C0 = 700 mg/L, pH = 8), and crystalline violet (CV, C0 = 500 mg/L, pH = 7) were 6501.09, 2870.30, 554.93, 6277.72, 626.50, and 3539.34 mg/g, respectively. The pseudo-second-order model and the Langmuir isotherm model were compatible with the experimental findings, which suggested the dominance of ion exchange and chemisorption. The materials were characterized by using XRD, SEM, FTIR, BET, and XPS, and the results showed that OBC had an outstanding specific surface area (2063 m2·g-1), with potential adsorption mechanisms that included electrostatic mechanisms, hydrogen bonding, and π-π adsorption. The fact that the adsorption capacity did not drastically decrease after five cycles of adsorption and desorption suggests that OBC has the potential to be a dye adsorbent.

Facile synthesis of chlorella-derived autogenous N-doped porous biochar for adsorption on tetracycline

In this study, an autogenous N-doped biochar derived from Chlorella (CVAC) was prepared with NaOH as activator at 800 °C. The surface structural properties of CVAC and the adsorption performance of CVAC on tetracycline (TC) under different adsorption variables were analyzed and investigated using different characterization methods. The results showed that the specific surface area of CVAC was 491.16 m² g^-1 and the adsorption process was in accordance with Freundlich model and pseudo-second-order kinetic model. The maximum adsorption capacity of TC was 310.696 mg g^-1 at pH 9 and 50 °C, and it was mainly physical adsorption. Furthermore, the cyclic adsorption-desorption behavior of CVAC using ethanol as eluent was evaluated and the feasibility of its long-term application was explored. CVAC also showed good cyclic performance. The variation of ΔG° and ΔH° confirmed that the adsorption of TC by CVAC was a spontaneous heat absorption process.

Copyrolysis of microalga Chlorella sp. and alkali lignin with potassium carbonate impregnation for synergistic Bisphenol A plasticizer adsorption

Composite functional materials offer promising opportunities for the development of tailored adsorbents with enhanced bioremediation potential towards toxic, carcinogenic endocrine disrupters such as Bisphenol A (BPA). Copyrolysis of microalga Chlorella sp. (CH) alkali lignin (L) with K₂CO₃ impregnation yielded a carbon-based composite (CHL-AC) with a micro-mesoporous structure of 0.643 cm³/g, surface area of 1414 m²/g, and BPA adsorption capacity of Q_max 316.858 mg/g. Enhanced BPA removal efficiency indicated a positive synergistic effect upon a combination of L and CH, resulting in a 73.24 % removal efficiency compared with the individual carbon components of 52.33 % for L-AC and 67.35 % for CH-AC. The kinetics and equilibrium results were described well by the pseudo second-order kinetic model and Freundlich isotherm, respectively. This paper elucidates the blending of microalgae and lignin into high-value carbon composite material, CHL-AC, with immense potential for the treatment of BPA-contaminated waters to contribute to Goal 6 (clean water and sanitation).

Preparation and characterization of low-cost activated carbon from Moringa oleifera chemically activated using ZnCl2 for the adsorption of bisphenol A

The use of agricultural by-products such as Moringa oleifera plants is one effort to support the reduction of environmental pollution. Activated carbon produces from agricultural wastes is relatively less expensive and can replace traditional methods such as renewable as well as nonrenewable materials such as petroleum residue and coal. In this study, the removal of bisphenol A from aqueous media was studied using activated carbon produced from M. oleifera pods and peels. A batch adsorption study was carried out by varying the parameters of the adsorption process. A maximum removal percentage of 95.46% was achieved at optimum conditions of 2.5 g L^-1 adsorbent dose, pH 7, 60 min contact time and 20 mg L^-1 initial concentration of BPA. The BET surface areas of MOP, MOP-AC and MOP-ACZ were found to be 12.60, 4.10 and 45.96 m²/g, respectively. The experimental data were analyzed by Langmuir, Freundlich and Temkin adsorption isotherm models. Equilibrium data fitted well with the Langmuir isotherm with a maximum monolayer adsorption capacity of 20.14 mg g^-1. The rates of adsorption were found to conform to the pseudo-second-order kinetics with a good correlation. The results indicate that the M. oleifera activated carbon could be employed as a low-cost alternative to commercial activated carbon in the removal of BPA from water.

Adsorption of Non-Steroidal Anti-Inflammatory Drugs on Alginate-Carbon Composites-Equilibrium and Kinetics

In this work, alginate-carbon composites with different active carbon content were synthesized and studied by various techniques. The obtained materials can be used as adsorbents in the processes of removing organic pollutants from water. In this study, the effect of the immobilization of activated carbon in calcium alginate was investigated. Textural properties were determined by measuring low-temperature nitrogen adsorption/desorption isotherms. The largest specific surface area was recorded for ALG_C8 and amounted to 995 m²/g. The morphology of alginate materials was determined on the basis of scanning electron microscopy. The adsorption properties were estimated based on the measurements of equilibrium and adsorption kinetics. The highest sorption capacities were 0.381 and 0.873 mmol/g for ibuprofen and diclofenac, respectively. The generalized Langmuir isotherm was used to analyze the equilibrium data. A number of equations and kinetic models were used to describe the adsorption rate data, including first (FOE) and second (SOE) order kinetic equations, 1,2-mixed-order kinetic equation (MOE), fractal-like MOE equation (f-MOE), multi-exponential equation (m-exp), in addition to diffusion models: intraparticle diffusion model (IDM) and pore diffusion model (PDM). Thermal stability was determined on the basis of data from thermal analysis in an atmosphere of synthetic air.

Carbon-based nanocomposite materials with multifunctional attributes for environmental remediation of emerging pollutants

Carbon-based materials are among the most biosynthesized nanocomposites with excellent tunability and multifunctionality features, that other materials fail to demonstrate. Naturally occurring materials, such as alginate (Alg), can be combined and modified by linking the active moieties of various carbon-based materials of interest, such as graphene oxide (GO), carbon nanotubes (CNTs), and mesoporous silica nanocomposite (MSN), among others. Thus, several types of robust nanocomposites have been fabricated and deployed for environmental remediation of emerging pollutants, such as pharmaceutical compounds, toxic dyes, and other environmentally hazardous contaminants of emerging concern. Considering the above critiques and added features of carbon-based nanocomposites, herein, an effort has been made to spotlight the synergies of GO, CNTs, and MSN with Alg and their role in mitigating emerging pollutants. From the information presented in this work, it can be concluded that Alg is a material that has excellent potential. However, its use still requires further tests in different areas and other materials to carry out a holistic investigation that exploits its versatility for environmental remediation purposes.

Highly efficient adsorption of Bisphenol A using NaHCO3/CO2 activated carbon composite derived from shrimp shell@cellulose

In this study, the efficiency of activated carbon (AC) synthesized from the shrimp shell plus cellulose (SS@C) was optimized toward Bisphenol A (BPA) adsorption. Low-cost, renewable, and non-toxic shrimp shells mixed with cellulose were carbonized, followed by activation via CO₂ and NaHCO₃ to produce SS@C-AC. The results revealed that SS@C-AC samples were a porous composite with mesoporous structures comprising a relatively high specific surface area (935.20 m²/g) with a mean pore size of around 3.8 nm and mesoporous volume of 1.83E-02 cm³/g. The influences of initial concentrations, pH values, and adsorption on BPA were investigated systematically. Isotherm model and kinetics study of the adsorption of BPA on SS@C-AC exhibited that the obtained data were in agreement with the Langmuir adsorption isotherm model while there is no difference between PFO and PSO kinetic results for BPA concentrations in the range 25-100 mg/L. The impregnation ratio of 1.5 NaHCO₃ and an activation time of 90 min at 800°C were the optimum conditions under which BPA removal of 81.78% was obtained.

Fabrication of Janus-type nanocomposites from cellulose nanocrystals for self-healing hydrogels' flexible sensors

Janus bio-nanomaterials have great application potential in functional solid surfactants, probes and flexible sensors. In this manuscript, the sustainable Janus cellulose nanocrystals-type (CNCs-type) nanomaterials were prepared by Pickering emulsion template method. The asymmetric functionalism of Janus nanorods was realized by asymmetrically grafting polypyrrole (PPy) and polydopamine (PDA) onto different sides of CNCs (Janus CNCs-PPy /PDA (JCNs)). JCNs was successfully applied to self-healing nanocomposite hydrogels and further applied to the development of flexible sensors. The self-healing efficiency of nanocomposite hydrogels was 87.2%, and the stress and strain reached 3.50 MPa and 453.45%, respectively. It is worth noting that flexible sensors have been widely used in the field of wearable electronic sensing for real-time monitoring of human movement due to their high sensitivity (gauge factor (GF) = 9.9) and fast response time (260 ms).

Self-regeneration hybrid hydrogel for bisphenol a adsorption in water

Hybrid hydrogel was synthesized by immobilizing TiO₂ in polyethylene glycol diacrylate (TiO₂@PEGDA) as an efficient adsorbent with photocatalysis property for bisphenol A (BPA) elimination. TiO₂@PEGDA exhibited spherical and rough structure with limited crystallinity and abundant functional groups. The contact angle increased to 61.96° (TiO₂@PEGDA) from 46.73° (pristine PEGDA), indicating that hydrogel hydrophilicity decreased due to the presence of TiO₂. The swelling capacity of TiO₂@PEGDA (9.0%) was decreased compared with pristine PEGDA (15.6%). Adsorption results demonstrated that the maximum adsorption capacity of TiO₂@PEGDA (101.4 mg/g) for BPA was slightly higher than that of pristine PEGDA (97.68 mg/g). The adsorption capacity was independent with pH below 8 and decreased obviously when the value of pH was higher than 8. The adsorption behavior was fitted well with the pseudo-second-order kinetic and the Langmuir isotherm model. Both ΔG₀ and ΔH₀ were negative, indicating that BPA adsorbed on TiO₂@PEGDA was an exothermic and spontaneous process. Regeneration study was performed by photocatalysis, and the adsorption capacity was 85.6% compared with the initial capacity after four-cycle use, indicating that TiO₂@PEGDA could be recycled without significant adsorption capacity loss. Consequently, TiO₂@PEGDA can serve as an eco-friendly and promising material for efficiently adsorbing BPA with self-clean property.

Adsorption modeling, thermodynamics, and DFT simulation of tetracycline onto mesoporous and high-surface-area NaOH-activated macroalgae carbon

Activated carbon (ENAC) was prepared by NaOH activation, using macroalgae (Enteromorpha clathrate) as raw material. The prepared activated carbon has a large surface area (1238.491 m² g^-1) and its total pore volume and average pore size are 0.6823 cm³g^-1 and 2.2038 nm, respectively. The ENAC was characterized by SEM, FTIR, BET and XPS. The effects of contact time (0-960 min), initial tetracycline (TC) concentration (50-500 mg L^-1), temperature (30-50 °C) and initial pH (2-11) on TC adsorption were evaluated. The adsorption isotherm and adsorption kinetics were discussed. Results showed that the adsorption isotherm was the Langmuir model, and the adsorption process can be described by the pseudo-second-order model. The N₂ adsorption-desorption isotherm was type IV, indicating that the activated carbon had mesoporous structure. Thermodynamic analysis showed that the adsorption process was endothermic and spontaneous. The maximum adsorption capacity of TC was 381.584 mg g^-1. Density functional theory (DFT) was used to simulate and analyze the adsorption process, and the influence of different types of N on the adsorption was expounded. The results showed that there are electrostatic interactions, π-π interactions and hydrogen bonding between the adsorbent and TC. These results indicated that the prepared ENAC had a great application prospect in the removal of antibiotics from aqueous solution.

Synthesis and characterisation of zinc oxide modified biorenewable polysaccharides based sustainable hydrogel nanocomposite for Hg2+ ion removal: Towards a circular bioeconomy

Industrial metal ion pollution has been considered the chief source of water contaminants all over the world. In the present research, we have prepared gum tragacanth cross-linked 2-hydroxyethyl methacrylate-co-acrylamide (GT-cl-(HEMA-co-AAm)) hydrogel and gum tragacanth cross-linked 2-hydroxyethyl methacrylate-co-acrylamide/zinc oxide (GT-cl-(HEMA-co-AAm)/ZnO) hydrogel composite with better Hg²⁺ adsorption capability. GT-cl-(HEMA-co-AAm)/ZnO hydrogel composite (154.8 mg g^-1) exhibited higher Hg²⁺ adsorption than GT-cl-(HEMA-co-AAm) hydrogel. To address the performance of GT-cl-(HEMA-co-AAm) hydrogel and GT-cl-(HEMA-co-AAm)/ZnO hydrogel composite, batch adsorption experiments were successfully conducted under different optimised conditions. At last, in-vitro antibacterial activities of Hg²⁺ loaded GT-cl-(HEMA-co-AAm) and GT-cl-(HEMA-co-AAm)/ZnO were performed in two different well Staphylococcus aureus (gram-positive) and Pseudomonas aeruginosa (gram-negative) bacteria. As a positive control, ampicillin was employed against both types of bacteria. This methodology for the reusability of material has a great ecofriendly impression for minimising secondary waste derived from adsorption and can help design upgraded antibacterial agents.

Raman Spectroscopy Characterization of Amorphous Coke Generated in Industrial Processes

Examples on the real-world field application of Raman spectroscopy with systematic analysis of the intensity variation of D and G bands corresponding to the change of excitation laser energy to characterize and compare coke species from various industrial processes are presented. The findings indicate the different degree of sp² and sp³ hybridized bonding structures of amorphous carbon collected from different industrial processes as well as heavy carbonaceous deposits generated by industrial catalysts. This spectroscopic methodology is practical and highly beneficial in identifying coke formation mechanisms in industrial processes, as well as supporting design strategies to abate the undesired coke formation on industrial catalysts.