Honeycomb-like cork activated carbon with ultra-high adsorption capacity for anionic, cationic and mixed dye: Preparation, performance and mechanism

Molecular simulation-based insights into dye pollutant adsorption: A perspective review

Growing concerns about environmental pollution have highlighted the need for efficient and sustainable methods to remove dye contamination from various ecosystems. In this context, computational methods such as molecular dynamics (MD), Monte Carlo (MC) simulations, quantum mechanics (QM) calculations, and machine learning (ML) methods are powerful tools used to study and predict the adsorption processes of dyes on various adsorbents. These methods provide detailed insights into the molecular interactions and mechanisms involved, which can be crucial for designing efficient adsorption systems. MD simulations, detailing molecular arrangements, predict dyes' adsorption behaviour and interaction energies with adsorbents. They simulate the entire adsorption process, including surface diffusion, solvent layer penetration, and physisorption. QM calculations, especially density functional theory (DFT), determine molecular structures and reactivity descriptors, aiding in understanding adsorption mechanisms. They identify stable adsorption configurations and interactions like hydrogen bonding and electrostatic forces. MC simulations predict equilibrium properties and adsorption energies by sampling molecular configurations. ML methods have proven highly effective in predicting and optimizing dye adsorption processes. These models offer significant advantages over traditional methods, including higher accuracy and the ability to handle complex datasets. These methods optimize adsorption conditions, clarify adsorbent functionalization roles, and predict dye removal efficiency under various conditions. This research explores MD, MC, QM, and ML approaches to connect molecular interactions with macroscopic adsorption phenomena. Probing these techniques provides insights into the dynamics and energetics of dye pollutants on adsorption surfaces. The findings will aid in developing and optimizing new materials for dye removal. This review has significant implications for environmental remediation, offering a comprehensive understanding of adsorption at various scales. Merging microscopic data with macroscopic observations enhances knowledge of dye pollutant adsorption, laying the groundwork for efficient, sustainable removal technologies. Addressing the growing challenges of ecosystem protection, this study contributes to a cleaner, more sustainable future.

Robust nanoparticles growth in the interior of porous sponges for efficient dye adsorption and emulsion separation

Emulsified oils and dye contaminants already pose a huge threat to global ecosystems and human health. It is a significant research topic to develop efficient, rapid, versatile methods for emulsion separation and dye adsorption. The membrane material modified with common methods only modified the outer surface of the membrane, while the interior is hardly fully decorated. In this investigation, a solvent exchange method was used to in situ grow nanoparticles in the interior of a porous sponge. These nanoparticles were obtained with polyethyleneimine, gallic acid, and tannic acid via Michael addition and Schiff base reaction. The prepared nanoparticle-coated sponges provided efficient separation of dyes, emulsions, and complex contaminants. The separation efficiency of the dye reached 99.49%, and the separation efficiency of the emulsion was as high as 99.87% with a flux of 11140.3 L m-2 h-1. Furthermore, the maximum adsorption capacity reached 486.8 mg g-1 for cationic dyes and 182.1 mg g-1 for anionic dyes. More importantly, the nanoparticles were highly robust on the surface of the porous sponge, and the modified sponge could have long-term applications in hazardous environments. Overall, it is envisioned that the nanoparticles-modified porous sponge exhibited considerable potential for emulsion and dye wastewater treatment.

A review on sustainable management of biomass: physicochemical modification and its application for the removal of recalcitrant pollutants-challenges, opportunities, and future directions

Adsorption is one of the most efficient methods for remediating industrial recalcitrant wastewater due to its simple design and low investment cost. However, the conventional adsorbents used in adsorption have several limitations, including high cost, low removal rates, secondary waste generation, and low regeneration ability. Hence, the focus of the research has shifted to developing alternative low-cost green adsorbents from renewable resources such as biomass. In this regard, the recent progress in the modification of biomass-derived adsorbents, which are rich in cellulosic content, through a variety of techniques, including chemical, physical, and thermal processes, has been critically reviewed in this paper. In addition, the practical applications of raw and modified biomass-based adsorbents for the treatment of industrial wastewater are discussed extensively. In a nutshell, the adsorption mechanism, particularly for real wastewater, and the effects of various modifications on biomass-based adsorbents have yet to be thoroughly studied, despite the extensive research efforts devoted to their innovation. Therefore, this review provides insight into future research needed in wastewater treatment utilizing biomass-based adsorbents, as well as the possibility of commercializing biomass-based adsorbents into viable products.

Optimization of hydrothermal synthesis conditions of Bidens pilosa-derived NiFe2O4@AC for dye adsorption using response surface methodology and Box-Behnken design

The presence of stable and hazardous organic dyes in industrial effluents poses significant risks to both public health and the environment. Activated carbons and biochars are widely used adsorbents for removal of these pollutants, but they often have several disadvantages such as poor recoverability and inseparability from water in the post-adsorption process. Incorporating a magnetic component into activated carbons can address these drawbacks. This study aims to optimizing the production of NiFe2O4-loaded activated carbon (NiFe2O4@AC) derived from a Bidens pilosa biomass source through a hydrothermal method for the adsorption of Rhodamine B (RhB), methyl orange (MO), and methyl red (MR) dyes. Response surface methodology (RSM) and Box-Behnken design (BBD) were applied to analyze the key synthesis factors such as NiFe2O4 loading percentage (10-50%), hydrothermal temperature (120-180 °C), and reaction time (6-18 h). The optimized condition was found at a NiFe2O4 loading of 19.93%, a temperature of 135.55 °C, and a reaction time of 16.54 h. The optimum NiFe2O4@AC demonstrated excellent sorption efficiencies of higher than 92.98-97.10% against all three dyes. This adsorbent was characterized, exhibiting a well-developed porous structure with a high surface area of 973.5 m2 g-1. Kinetic and isotherm were studied with the best fit of pseudo-second-order, and Freundlich or Temkin. Qmax values were determined to be 204.07, 266.16, and 177.70 mg g-1 for RhB, MO, and MR, respectively. By selecting HCl as an elution, NiFe2O4@AC could be efficiently reused for at least 4 cycles. Thus, the Bidens pilosa-derived NiFe2O4@AC can be a promising material for effective and recyclable removal of dye pollutants from wastewater.

Baking-inspired pore regulation strategy towards a hierarchically porous carbon for ultra-high efficiency cationic/anionic dyes adsorption

Converting waste resource into porous carbon toward contaminant capturing is a crucial strategy for realizing "treating waste with waste". Inspired by bread baking process, the soybean meal activated carbon (SAC) with multimodal pore structures was developed via thermally remodeling the pores of waste soybean meal. The obtained SAC-3-800 has ultra-high specific surface area (3536.952 m2/g), as well as a hierarchically porous structure. SAC-3-800 exhibits extremely high adsorption capacity for methylene blue (MB) (3015.59 mg/g), methyl orange (MO) (6486.30 mg/g), and mixed dyes (8475.09 mg/g). The hierarchically porous structure enabled fast adsorption kinetics of SAC-3-800 for MB and MO (∼30 min). Additionally, SAC-3-800 shows excellent dynamic adsorption and regeneration performance, exhibiting great potential for industrial applications. This work showcases a feasible method for synthesizing hierarchically porous carbon with outstanding adsorption performance that can simultaneously achieve efficient treatment of dye-wastewater and value-added utilization of waste resources.

Conversion of waste cork to N-doped porous carbons by urea-assisted hydrothermal method for enhanced VOC capture

Converting waste resources into porous carbon for pollutants capture is an effective strategy to achieve the environmental goal of "treating waste with waste". Cork is an ideal precursor of porous carbons due to its ordered honeycomb-like cell structure and layered composition distribution. Herein, N-doped porous carbons (PCs) were prepared via two steps of urea-assisted hydrothermal carbonization and chemical activation to mitigate volatile organic compounds (VOCs) pollution. Results indicated that the obtained PC4-800 exhibited remarkable features for adsorption including high total pore volume (0.97 cm3/g) and specific surface area (1864.89 m2/g), as well as abundant N-containing functional groups. The excellent pore structure was primarily owing to the corrosion of the carbon matrix by the gas produced from the reaction of K2CO3 and N-containing functional groups. The adsorption results showed that the PC4-800 have an outstanding toluene adsorption capacity (867.03 mg/g) that outperforming majority of adsorbents previously reported. There are substantial pores in N-doped PCs with a pore width of 1.71-2.28 nm, which is 3 to 4 times the molecular dynamic diameter of toluene, and plays a crucial role in the absorption process. Moreover, the promotional influence of N-functional groups on the toluene adsorption process was verified through DFT calculation by Gaussian imitating, where N-6 generated π-electron enrichment sites on the surface of N-doped PCs, facilitating π-π dispersion with the benzene ring in toluene. This study provides a new strategy to convert waste cork into high-performance adsorbents for VOCs removal.

Magnetic activated carbon from spent coffee grounds: iron-catalyzed CO2 activation mechanism and adsorption of antibiotic lomefloxacin from aqueous medium

The facile fabrication of low-cost adsorbents possessing high removal efficiency and convenient separation property is an urgent need for water treatment. Herein, magnetic activated carbon was synthesized from spent coffee grounds (SCG) by Fe-catalyzed CO2 activation at 800 °C for 90 min, and magnetization and pore formation were simultaneously achieved during heat treatment. The sample was characterized by N2 adsorption-desorption, XRD, VSM, SEM, and FTIR. Batch adsorption experiments were conducted using lomefloxacin (LMO) as the probing pollutant. Preparation mechanism was revealed by TG-FTIR and XRD. Experimental results showed that Fe3O4 derived from Fe species can be reduced to Fe by carbon at high temperatures, followed by subsequent reoxidation to Fe3O4 by CO2, and the redox cycle between Fe and Fe3O4 favored the formation of pores. The promotion effects of Fe species on CO2 activation can be quantitatively reflected by the yield of CO as the signature gaseous product, and the suitable activation temperate range was determined to be 675 to 985 °C. The BET surface area, total pore volume, and saturated magnetization value of the product were 586 m2 g-1, 0.327 cm3 g-1, and 11.59 emu g-1, respectively. The Langmuir model was applicable for the adsorption isotherm data for LMO with the maximum adsorption capacity of 95 mg g-1, and thermodynamic analysis revealed that the adsorption process was endothermic and spontaneous. This study demonstrated that Fe-catalyzed CO2 activation was an effective method of converting SCG into magnetic separable adsorbent for LMO removal from aqueous medium.

Compressible polydopamine modified pomelo peel powder/poly(ethyleneimine)/κ-carrageenan aerogel with pH-tunable charge for selective removal of anionic and cationic dyes

In this work, a novel biomass-based aerogel, polydopamine decorated pomelo peel powder/polyethyleneimine/κ-carrageenan (PPEKC) aerogel, was developed for dye wastewater treatment. The as-prepared PPEKC aerogel possessed a robust structure and good compressible resilience. As expected, this aerogel presented remarkable efficacy in eliminating both anionic and cationic dyes. The experimental maximum adsorption capacities were 2016.7 mg g-1 for congo red (CR) at pH = 5 and 1176.6 mg g-1 for methylene blue (MEB) at pH = 11, following with ultra-fast adsorption rates. The adsorption kinetics followed the pseudo-second-order model. The adsorption isotherms exhibited a stronger alignment with the Langmuir isotherm model for CR at 308 K and MEB at 288, 298, 308 K. The Freundlich isotherm model yielded a suitable fit for the adsorption of CR at 288 and 298 K. Thermodynamic analyses indicated that the removal of CR and MEB was spontaneous and endothermic. The adsorption mechanisms involved electrostatic interactions, π-π interactions, and hydrogen bonds. Intriguingly, it could achieve bidirectional selective adsorption of anionic and cationic dyes in the designed pH values, due to pH-tunable surface charge. Additionally, it also exhibited favorable reusability and antibacterial activity. Therefore, the as-prepared PPEKC aerogel could be a promising biosorbent for dye wastewater treatment.

Preparation of Bamboo-Based Activated Carbon via Steam Activation for Efficient Methylene Blue Dye Adsorption: Modeling and Mechanism Studies

Dye pollution has long been an ecological and human health issue. Activated carbon is considered to be the most promising material for dye adsorption. In this study, bamboo was used as a biomass precursor to produce activated carbon with a high specific surface area by the steam activation method. The physical activation reaction between water vapor and bamboo promotes the carbonization product to have a rich porous structure. The prepared activated carbon was investigated from the perspectives of surface morphology, elemental change, surface porosity, and surface functional groups using a variety of techniques. According to the Brunauer-Emmett-Teller analysis, the activated carbon has a high surface area (1273 m2/g) and a mesoporous structure (average pore size 3.1 nm). On this basis, the effect of activated carbon on the removal of methylene blue (MB) dye from aqueous environments was evaluated and optimized by response surface methodology (RSM). Key adsorption parameters include initial MB concentration (150-200 mg/L), adsorption time (5-120 min), adsorbent dosage (30-50 mg), adsorption temperature (5-50 °C), and solution pH (3-11). Box-Behnken design (BBD) was used for modeling and analysis. Kinetic and isotherm model studies show that pseudo-second-order model kinetics and Langmuir isotherm can better describe the process of MB dye adsorption. This study will provide new ideas for the preparation of bamboo-activated carbon and provide a model prediction basis for dye adsorption research.

Efficient and Selective Adsorption of Cationic Dye Malachite Green by Kiwi-Peel-Based Biosorbents

In this study, pristine kiwi peel (KP) and nitric acid modified kiwi peel (NA-KP) based adsorbents were prepared and evaluated for selective removal of cationic dye. The morphology and chemical structure of KP and NA-KP were fully characterized and compared, and results showed nitric acid modification introduced more functional groups. Moreover, the adsorption kinetics and isotherms of malachite green (MG) by KP and NA-KP were investigated and discussed. The results showed that the adsorption process of MG onto KP followed a pseudo-second-order kinetic model and the Langmuir isotherm model, while the adsorption process of MG onto NA-KP followed a pseudo-first-order kinetic model and the Freundlich isotherm model. Notably, the Langmuir maximum adsorption capacity of NA-KP was 580.61 mg g^-1, which was superior to that of KP (297.15 mg g^-1). Furthermore, thermodynamic studies demonstrated the feasible, spontaneous, and endothermic nature of the adsorption process of MG by NA-KP. Importantly, NA-KP showed superior selectivity to KP towards cationic dye MG against anionic dye methyl orange (MO). When the molar ratio of MG/MO was 1:1, the separation factor (α_MG/MO) of NA-KP was 698.10, which was 5.93 times of KP. In addition, hydrogen bonding, π-π interactions, and electrostatic interaction played important roles during the MG adsorption process by NA-KP. This work provided a low-cost, eco-friendly, and efficient option for the selective removal of cationic dye from dyeing wastewater.

Preparation of a highly functionalized activated carbon from waste third-monomer pressure filter liquid for removal of methylene blue in aqueous solution

Third monomer dimethyl isophthalate-5-sodium sulfonate (SIPM) is an additive widely used to modify polyester chips. During the manufacture of SIPM, large amounts of waste third-monomer pressure filter liquid are produced. As the liquid contains lots of toxic organics and highly concentrated Na₂SO₄, it will cause serious environmental pollution if discharged directly. In this study, highly functionalized activated carbon (AC) was prepared by directly carbonizing the dried waste liquid under ambient pressure. Structural and adsorption properties of the prepared AC were analyzed and evaluated by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), N₂ adsorption-desorption analysis and methylene blue (MB) as the adsorbate, respectively. Results showed that the adsorption capacity of the prepared AC to MB reached the highest when carbonization was conducted at 400 °C. XRD analysis showed that the AC has a disordered graphite-like crystal structure. FT-IR and XPS analyses showed that there were plenty of carboxyl and sulfonic functional groups in the AC. The adsorption follows the pseudo-second-order kinetic model and the isotherm process is consistent with the Langmuir model. The adsorption capacity increased with increasing solution pH and dropped when the solution pH exceeded 12. Increasing solution temperature favors the adsorption, where the maximum value can reach as high as 2816.4 mg g^-1 at 45 °C, more than double the values reported to date. The adsorption of MB on the AC is mainly controlled by the electrostatic interaction between MB and the anionic form of carboxyl and sulfonic groups.

Preparation of Reusable Porous Carbon Nanofibers from Oxidized Coal Liquefaction Residue for Efficient Adsorption in Water Treatment

Porous carbon nanofibers are commonly used for adsorption processes owing to their high specific surface area and rich pore structure. However, the poor mechanical properties of polyacrylonitrile (PAN)-based porous carbon nanofibers have limited their applications. Herein, we introduced solid waste-derived oxidized coal liquefaction residue (OCLR) into PAN-based nanofibers to obtain activated reinforced porous carbon nanofibers (ARCNF) with enhanced mechanical properties and regeneration for efficient adsorption of organic dyes in wastewater. This study examined the effects of contact time, concentration, temperature, pH, and salinity on the adsorption capacity. The adsorption processes of the dyes in ARCNF are appropriately described by the pseudo-second-order kinetic model. The maximum adsorption capacity for malachite green (MG) on ARCNF is 2712.84 mg g^-1 according to the fitted parameters of the Langmuir model. Adsorption thermodynamics indicated that the adsorptions of the five dyes are spontaneous and endothermic processes. In addition, ARCNF have good regenerative performance, and the adsorption capacity of MG is still higher than 76% after 5 adsorption-desorption cycles. Our prepared ARCNF can efficiently adsorb organic dyes in wastewater, reducing the pollution to the environment and providing a new idea for solid waste recycling and water treatment.

Construction of Cu-N coordination into natural biopolymer lignin backbone for highly efficient and selective removal of cationic dyes

Here, a Cu²⁺-doped lignin-based adsorbent (Cu-AL) was fabricated via the amination and Cu²⁺-doping of industrial alkali lignin for massive and selective adsorption of cationic dyes azure B (AB) and saffron T (ST). The Cu-N coordination structures endowed Cu-AL with stronger electronegativity and higher dispersity. Through the electrostatic attraction, π-π interaction, H-bonding, and Cu²⁺ coordination, the adsorption capacities of AB and ST reached up to 1168 and 1420 mg g^-1, respectively. The pseudo-second-order model and Langmuir isotherm model were more relevant to the AB and ST adsorption on Cu-AL. Based on the thermodynamic study, the adsorption progresses were endothermic, spontaneous, and feasible. The Cu-AL maintained high removal efficiency to dyes after 4 reuses (>80%). Importantly, the Cu-AL could efficiently remove and separate AB and ST from dye mixtures even in real time. All the above characteristics demonstrated that Cu-AL was an excellent adsorbent for fast wastewater treatment.

Efficient removal of Congo red and methylene blue using biochar from Medulla Tetrapanacis modified by potassium carbonate

Biochar (BC) prepared from Medulla Tetrapanacis was recognized as having potential in environmental remediation because of its porous texture, abundant chemical surface groups and mineral composition. In this study, a novel modified biochar (KBC) derived from Medulla Tetrapanacis achieved efficient adsorption of Congo red (CR) and methylene blue (MB). Characterization results suggested that the modification had little effect on the group distribution of KBC, but a dramatic expansion of specific surface area was observed on KBC (1180.45 m2/g) compared to BC (198.51 m2/g). KBC exhibited a maximum sorption of 584.17 mg/g for CR and 318.01 mg/g for MB. Kinetic and isotherm studies revealed sorption of CR and MB by KBC was chemosorption, which occurred on the monolayer surface. The comprehensive analysis also provided the basis for the application of KBC to practical production. These outcomes suggested that KBC may become a new option for the effluent treatment.

Brilliant blue FCF dye adsorption using magnetic activated carbon from Sapelli wood sawdust

Sapelli wood sawdust-derived magnetic activated carbon (SWSMAC) was produced by single-step pyrolysis using KOH and NiCl₂ as activating and magnetization agents. SWSMAC was characterized by several techniques (SEM/EDS, N₂ adsorption/desorption isotherms, FTIR, XRD, VSM, and pH_PZC) and applied in the brilliant blue FCF dye adsorption from an aqueous medium. The obtained SWSMAC was a mesoporous material and showed good textural properties. Metallic nanostructured Ni particles were observed. Also, SWSMAC exhibited ferromagnetic properties. In the adsorption experiments, adequate conditions were an adsorbent dosage of 0.75 g L^-1 and a solution pH of 4. The adsorption was fast, and the pseudo-second-order demonstrated greater suitability to the kinetic data. The Sips model fitted the equilibrium data well, and the maximum adsorption capacity predicted by this model was 105.88 mg g^-1 (at 55 °C). The thermodynamic study revealed that the adsorption was spontaneous, favorable, and endothermic. Besides, the mechanistic elucidation suggested that electrostatic interactions, hydrogen bonding, π-π interactions, and n-π interactions were involved in the brilliant blue FCF dye adsorption onto SWSMAC. In summary, an advanced adsorbent material was developed from waste by single-step pyrolysis, and this material effectively adsorbs brilliant blue FCF dye.

Rapid, Highly-Efficient and Selective Removal of Anionic and Cationic Dyes from Wastewater Using Hollow Polyelectrolyte Microcapsules

Herein, poly (allylamine hydrochloride) (PAH)/ poly (styrene sulfonic acid) sodium salt (PSS) microcapsules of (PAH/PSS)2PAH (P2P MCs) and (PAH/PSS)2 (P2 MCs) were obtained by a layer-by-layer method. The P2 MCs show high adsorption capacity for Rhodamine B (642.26 mg/g) and methylene blue (909.25 mg/g), with an extremely low equilibrium adsorption time (~20 min). The P2P MCs exhibited high adsorption capacities of reactive orange K-G (ROKG) and direct yellow 5G (DY5G) which were 404.79 and 451.56 mg/g. Adsorption processes of all dyes onto microcapsules were best described by the Langmuir isotherm model and a pseudo-second-order kinetic model. In addition, the P2P MCs loaded with reactive dyes (P2P–ROKG), could further adsorb rhodamine B (RhB) dye, and P2 MCs that had adsorbed cationic MB dyes could also be used for secondary adsorption treatment of direct dye waste-water, respectively. The present work confirmed that P2P and P2 MCs were expected to become an excellent adsorbent in the water treatment industry.

Adsorptive Features of Magnetic Activated Carbons Prepared by a One-Step Process towards Brilliant Blue Dye

Water pollution by dyes has been a major environmental problem to be tackled, and magnetic adsorbents appear as promising alternatives to solve it. Herein, magnetic activated carbons were prepared by the single-step method from Sapelli wood sawdust, properly characterized, and applied as adsorbents for brilliant blue dye removal. In particular, two magnetic activated carbons, MAC1105 and MAC111, were prepared using the proportion of biomass KOH of 1:1 and varying the proportion of NiCl₂ of 0.5 and 1. The characterization results demonstrated that the different proportions of NiCl₂ mainly influenced the textural characteristics of the adsorbents. An increase in the surface area from 260.0 to 331.5 m² g^-1 and in the total pore volume from 0.075 to 0.095 cm³ g^-1 was observed with the weight ratio of NiCl₂. Both adsorbents exhibit ferromagnetic properties and the presence of nanostructured Ni particles. The different properties of the materials influenced the adsorption kinetics and equilibrium of brilliant blue dye. MAC111 showed faster kinetics, reaching the equilibrium in around 10 min, while for MAC1105, it took 60 min for the equilibrium to be reached. In addition, based on the Sips isotherm, the maximum adsorption capacity was 98.12 mg g^-1 for MAC111, while for MAC1105, it was 60.73 mg g^-1. Furthermore, MAC111 presented the potential to be reused in more adsorption cycles than MAC1105, and the use of the adsorbents in the treatment of a simulated effluent exhibited high effectiveness, with removal efficiencies of up to 90%.

Noval green sodium alginate/gellan gum aerogel with 3D hierarchical porous structure for highly efficient and selective removal of Congo red from water

Rational design of adsorbed materials with three-dimensional (3D) hierarchical porous structure, sustainable, high adsorption capacity, and excellent selective is of great significance in practical applications. Herein, a novel aerogel adsorbed material with 3D hierarchical porous architecture was fabricated by employing naturally abundant sodium alginate (SA)/gellan gum (GG) as basic construction blocks to achieve sustainability as well as applying polyethyleneimine (PEI) as functional material for highly efficient and selective capture of Congo red (CR). The aerogel sorbent exhibited strong microstructure, numerous active adsorption sites and being ultralight. The resulting aerogel adsorbent showed high adsorption capacity (3017.23 mg/g) toward CR, exceedingly most previously reported sorbents. Furthermore, the aerogel adsorbent was accompanied by outstanding selectivity for CR in four binary dye systems. Meanwhile, after 3 cycles, the adsorption capacity decreased by 14.8 %, but still maintained the adsorption capacity of 559.79 mg/g. Therefore, excellent adsorption performance, and superb selectivity prefigures its great prospects for wastewater purification.

Olive mill wastewater from a liquid biological waste to a carbon/oxocalcium composite for selective and efficient removal of methylene blue and paracetamol from aqueous solution

In this study, a Carbon/Oxocalcium was prepared from olive mill wastewater and successfully applied to the removal of paracetamol and methylene blue (MB) from an aqueous medium. The optimized composite (0.3 % CaO) is rich in anionic sites, porous and has a specific surface area of about 1383 m².g^-1. Adsorption tests showed significant adsorption capacities up to 1141 mg.g^-1. The adsorption of MB and paracetamol is well described by the Redlich-Peterson and Dubinin-Radushkevich isotherm, respectively. Moreover, the adsorption kinetics fitted to pseudo-second order. The π -π interactions, hydrogen bonds and electrostatic interactions were responsible for the adsorption of paracetamol and MB substrates. This work develops by a single, easy and simple action a new effective and selective material for the removal of emerging pollutants, a new method for the development of more stable carbon composites and a cost-effective method for the valorization of olive mill wastewater.

Selenite elimination via zero-valent iron modified biochar synthesized from tobacco straw and copper slag: Mechanisms and agro-industrial practicality

Cost-effectively improving the performance of biochar is essential for its large-scale practical application. In this work, the agro-industrial by-products copper slag and tobacco straw were employed for the preparation of modified biochar (CSBC). The obtained CSBC exhibited satisfactory capacity on Se(IV) immobilization of 190.53 mg/g, with surface interactions determined by the monolayer and mainly chemisorption. The removal mechanisms included chemical reduction, electrostatic attraction, co-precipitation, and formation of complexations. Interestingly, the existence of Cu2Se structure after adsorption indicated the involvement of Cu species within Se(IV) elimination. Moreover, the industrial agricultural practicality of CSBC was evaluated by regeneration tests, economic assessment, and pot experiments. The results demonstrate that iron species-modified biochar prepared from two agro-industrial by-products is a promising and feasible candidate for selenite removal from wastewater.

3D Porous Structure-Inspired Lignocellulosic Biosorbent of Medulla tetrapanacis for Efficient Adsorption of Cationic Dyes

The focus of this work was on developing a green, low-cost, and efficient biosorbent based on the biological structure and properties of MT and applying it to the remediation of cationic dyes in dye wastewater. The adsorption performance and mechanism of MT on methylene blue (MB) and crystal violet (CV) were investigated by batch adsorption experiments. The results demonstrated that the highest adsorption values of MT for MB (411 mg/g) and CV (553 mg/g) were greatly higher than the reported values of other biosorbents. In addition, the adsorption behaviors of methylene blue (MB) and crystal violet (CV) by MT were spontaneous exothermic reactions and closely followed the pseudo-second-order (PSO) kinetics and Langmuir isotherm. Further, the depleted MT was regenerated using pyrolysis mode to convert depleted MT into MT-biochar (MBC). The maximum adsorption of Cu2+ and Pb2+ by MBC was up to 320 mg/g and 840 mg/g, respectively. In conclusion, this work presented a new option for the adsorption of cationic dyes in wastewater and a new perspective for the treatment of depleted biosorbents.