Insight into the adsorptive removal of ibuprofen using porous carbonaceous materials: A review

One-step carbonization/activation synthesis of chitosan-based porous sheet-like carbon and studies of adsorptive removal for Rhodamine B

In this work, new N, O-codoped chitosan-derived carbon adsorbents (CKC-x, x refer to the calcination temperature) were synthesized over a simple process of chitosan-KOH aerogel production and simultaneous carbonization/activation of the aerogel. CKC-700 was characterized by sheet-like morphology (even containing a portion of carbon nano-sheet of 3 nm thickness), high porosity and specific surface area (1702.1 m2/g), and pyridinic/pyrrolic/graphitic N groups. The simultaneous carbonization/activation of chitosan-KOH aerogel prepared by top-down coagulation of chitosan aqueous solution by KOH aqueous solution rendered these beneficial characteristics. CKC-700 exhibited a superior adsorption capacity for Rhodamine B (RhB) to other chitosan-derived carbon adsorbents, and the maximum adsorption capacity for RhB of 594 mg/g was achieved at 55 °C. CKC-700 also possessed reasonable reusability for the removal of RhB, and the removal efficiency was still above 95 % in the fifth cycle. The effects of adsorption temperature and time, adsorbent dose, organic dye concentration, and solution pH on the adsorption capacity of CKC-700 were studied. Moreover, the adsorption isotherm, kinetics, thermodynamics, and the adsorption mechanism of RhB on CKC-700 were discussed. In addition, CKC-700 also showed favorable adsorption performance for methylene blue (441 mg/g), methyl orange (457 mg/g), and congo red (500 mg/g) at around 25 °C.

Polyethyleneimine-functionalized magnetic sugarcane bagasse cellulose film for the efficient adsorption of ibuprofen

Polyethyleneimine-modified magnetic sugarcane bagasse cellulose film (P-SBC/Fe3O4 film) was simply fabricated for the removal of ibuprofen (IBP), a typical emerging organic contaminant. The P-SBC/Fe3O4 film exhibited an equilibrium adsorption amount of 370.52 mg/g for IBP and a corresponding removal efficiency of 92.63 % under following adsorption conditions: 318 K, pH 4, and 0.25 mg/mL dosage. Thermodynamic studies indicated that adsorption of IBP on the P-SBC/Fe3O4 film was spontaneous (∆G < 0) and endothermic (∆H > 0). The adsorption data conformed to the Freundlich isotherm model and multilayer adsorption model (two layers), and an average of 3-4 active sites on the P-SBC/Fe3O4 film share an IBP molecule. Both the EDR-IDR and AOAS models vividly described the dynamic characteristics of adsorption process. Model fitting results, theoretical calculations, and comprehensive characterization revealed that adsorption is driven by electrostatic interactions between the primary amine of P-SBC/Fe3O4 film and the carboxyl group of IBP molecule, while other weak interactions are also non-ignorable. Furthermore, quantitative calculations based on density functional theory (DFT) underscored the importance of PEI functionalization. In conclusion, P-SBC/Fe3O4 film is an environmentally friendly and cost-effective adsorbent with significant potential for effectively removing IBP, while maintaining its efficacy over multiple cycles.

Innovative strategies for enhancing gas separation: Ionic liquid-coated PES membranes for improved CO2/N2 selectivity and permeance

As a cost-effective advancement in membrane technology, this study investigates the impact of PEG additive and CBT on the structural, stability, and gas permeance properties of PES-coated membranes, utilizing 1-dodecyl-3-methylimidazolium chloride ionic liquid ([DDMI][Cl] IL) as a carrier liquid. BET and FT-IR analyses highlight the significant enhancement in performance through the immobilization of pores with [DDMIM][Cl] IL. The investigation focuses on PES-M5-coated membranes, revealing excellent stability in finger-like pore structures prepared through direct immersion and nitrogen pressure immobilization. PES-M5-coated membranes with [DDMIM][Cl] IL via direct immersion experience lower weight loss than those coated using nitrogen pressure, with critical pressures at 1.4 and 1.25 bar, respectively. The study identifies PES-coated membranes, particularly PES-M25 (20.88 GPU) with macro-void pores and PES-M5 (29 GPU) with finger-like pores, exhibiting the highest CO2 permeance and CO2/N2 selectivity. As a cost-effective advancement in membrane technology, ionic liquids are employed in support membranes to enhance gas separation. Employing pure PES membranes with varying pore structures, created through the NIPS method, the study immobilizes [DDMI][Cl] IL in membrane pores through nitrogen pressure and direct immersion. Results underscore the successful application of porous support materials coated with ionic liquids for continuous CO2 and sulfur compound separation, showcasing competitive permeability and selectivity compared to traditional polymer membranes.

Removal of Cr(VI) from aqueous solution using ball mill modified biochar: multivariate modeling, optimization and experimental study

Chromium (Cr(VI)) pollution has attracted wide attention due to its high toxicity and carcinogenicity. Modified biochar has been widely used in the removal of Cr(VI) in water as an efficient and green adsorbent. However, the existing biochar prepared by chemical modification is usually complicated in process, high in cost, and has secondary pollution, which limits its application. It is urgent to explore modified biochar with simple process, low cost and environmental friendliness. Therefore, ball milling wheat straw biochar (BM-WB) was prepared by ball milling technology in this paper. The adsorption characteristics and mechanism of Cr(VI) removal by BM-WB were analyzed by functional group characterization, adsorption model and response surface method. The results showed that ball milling effectively reduced the particle size of biochar, increased the specific surface area, and more importantly, enhanced the content of oxygen-containing functional groups on the surface of biochar. After ball milling, the adsorption capacity of Cr(VI) increased by 3.5-9.1 times, and the adsorption capacity reached 52.21 mg/g. The adsorption behavior of Cr(VI) follows the pseudo-second-order kinetics and Langmuir isotherm adsorption model rate. Moreover, the Cr(VI) adsorption process of BM-WB is endothermic and spontaneous. Under the optimized conditions of pH 2, temperature 45 °C, and adsorbent dosage 0.1 g, the removal rate of Cr(VI) in the solution can reach 100%. The mechanism of Cr(VI) adsorption by BM-WB is mainly based on electrostatic attraction, redox and complexation. Therefore, ball milled biochar is a cheap, simple and efficient Cr(VI) removal material, which has a good application prospect in the field of remediation of Cr(VI) pollution in water.

Development of calcium phosphate-chitosan composites with improved removal capacity toward tetracycline antibiotic: Adsorption and electrokinetic properties

Two eco-friendly and highly efficient adsorbents, namely brushite-chitosan (DCPD-CS), and monetite-chitosan (DCPA-CS) composites were synthesized via a simple and low-cost method and used for tetracycline (TTC) removal. The removal behavior of TTC onto the composite particles was studied considering various parameters, including contact time, pollutant concentration, and pH. The maximum TTC adsorption capacity was 138.56 and 112.48 mg/g for the DCPD-CS and DCPA-CS, respectively. Increasing the pH to 11 significantly enhanced the adsorption capacity to 223.84 mg/g for DCPD-CS and 205.92 mg/g for DCPA-CS. The antibiotic adsorption process was well-fitted by the pseudo-second-order kinetic and Langmuir isotherm models. Electrostatic attractions, complexation, and hydrogen bonding are the main mechanisms governing the TTC removal process. Desorption tests demonstrated that the (NH4)2HPO4 solution was the most effective desorbing agent. The developed composites were more efficient than DCPD and DCPA reference samples and could be used as valuable adsorbents of TTC from contaminated wastewater.

Important role of pore-filling mechanism in separating naproxen from water by micro-mesoporous carbonaceous material

Commercial micro-mesoporous carbonaceous material (MCM; 56.8% mesopores) was applied for investigating the removal phenomenon of naproxen drug in aqueous solutions through batch adsorption experiments. Results demonstrated that the adsorption capacity of MCM to naproxen was slightly affected by different pHeq (2.0-11) and ionic strength (0-1 M NaCl). Adsorption kinetics, isotherms, thermodynamics, and mechanisms were evaluated at pH 7.0. Adsorption kinetics indicated the rate constants for adsorption (0.2 × 10-3  L/(mg × min) and desorption (0.076/min) and the adsorption equilibrium constant (2.6 × 10-3  L/mg). Adsorption isotherm showed that MCM exhibited a high-affinity adsorption capacity to naproxen (even at low concentrations) and its Langmuir maximum adsorption capacity (Qmax ) was 252.7 mg/g at 25°C. Adsorption thermodynamics proved that the adsorption process was endothermic and physisorption (ΔH° = 9.66 kJ/mol). The analysis result of pore size distribution demonstrated that the internal pore structure of MCM was appropriate for adsorbing naproxen molecules. Pore-filing mechanism (pore diffusion phenomenon) was confirmed by a considerable decrease in BET-surface area (585 m2 /g) and total pore volume (0.417 cm3 /g) of MCM after adsorbing naproxen (~1000 mg/L and pH 7.0) at 5 min (341 and 0.256), 60 min (191 and 0.205), 120 min (183 and 0.193), 360 min (144 and 0.175), and 24 h (71.6 m2 /g and 0.123 cm3 /g, respectively). The pore diffusion occurred rapidly (even at the initial adsorption period of 5 min). The FTIR technique was applied to identify the existence of C-H···π and n-π interaction. π-π interaction (evaluated through ID /IG ratio and C=C band) played a minor contribution in adsorption mechanisms. The ID /IG ratio (determined by the Raman technique) of MCM before adsorption (1.195) was similar to that after adsorption (1.190), and the wavenumber (C=C band; its FTIR spectrum) slightly shifted from 1638 to 1634 cm-1 after adsorption. A decrease in the Qmax value of MCM from 249 to 217 (H2 O2 -oxidized MCM) or to 224 mg/g (HNO3 -oxidized MCM) confirmed the presence of π-π interaction. Electrostatic attraction was a minor contribution. MCM can serve as a promising material for removing naproxen from water environment through a pore-filling mechanism. PRACTITIONER POINTS: Pore-filling mechanism was proposed by comparing textural properties of MCM before and after adsorbing naproxen. C-H···π and n-π interactions were identified via FTIR technique. π-π interaction was observed by FTIR and Raman techniques. Oxidation of MCM with HNO3 or H2 O2 was a helpful method to explore π-π interaction. Electrostatic attraction was explained through studies: effects of pH and NaCl along with desorption.

Porous carbons prepared from a novel hard wood composite waste for effective adsorption of Pb(ii) and Cd(ii) ions

In our previous investigations, a hard wood composite (HWC) was formulated by adding rice straw, as a filler to the recycled polystyrene foam waste at mass ratio (50/50) at 170 °C and pressed under 40 kPa. Here, the disposed HWC product as a model scrap was applied for production of porous carbons enclosed with graphene sheets. To attain this approach, HWC was hydrothermally carbonized (S1) followed by either post-heat treatment (S2) or potassium hydroxide (KOH, S3) activation at 750 °C for 2 hours. The properties of prepared samples were evaluated using SEM, ATR-IR, and porosity measurements. The adsorption performance of the obtained porous carbons toward removal of lead (Pb(ii)) and cadmium (Cd(ii)) ions from aqueous solutions was investigated under different operating conditions like contact time, initial pH, initial metal ions concentration and adsorbent dose. Kinetic models such as pseudo-first order, pseudo-second order and intraparticle diffusion were used to analyze the adsorption data. Langmuir, Freundlich, Dubinin-Radushkevich and Redlich-Peterson isotherms were applied. Thermodynamics and regeneration studies were performed. The sample (S3) comprised a micro-mesoporous carbon structure encompassed by graphene sheets, with the largest total surface area (422 m2 g-1) and adsorption capacities for Pb(ii) and Cd(ii) ions of 207.9 and 119.6 mg g-1, respectively. The experimental adsorption data were best elucidated using Langmuir and pseudo second-order kinetic models. Thermodynamic experiments confirmed that adsorption is an endothermic and spontaneous process. Conclusively, the investigated HWC waste is a promising carbonaceous precursor for preparing effective porous graphene-carbons used in the removal heavy metals from their aqueous stream.

Green conversion of waste PET into magnetic Ni0·4Fe2·6O4/(Fe,Ni)@carbon nanostructure for adsorption and separation of dyes from aqueous media

A nanostructured core-shell composite (Ni0·4Fe2·6O4/(Fe,Ni)@carbon, NFC) comprising magnetic nano-cores encapsulated with graphitic shells (≈80 wt%) is prepared by facile and clean mechanochemical-molten salt processing approach using waste PET; providing a specific surface area of 201.9 m2 g-1, well-developed mesopores, and ferromagnetic behavior characterized by the coercivity value of 149 Oe. NFC is utilized as a high-performance adsorbent for the removal of organic dyes from their aqueous solutions. Moreover, the magnetic performance of NFC enables the facile collection of the exhausted adsorbent out of the purified water. Performances of NFC for the removal of crystal violet dye (CV), methyl orange (MO) and rhodamine B (Rh B) from their aqueous solutions are systematically investigated under different environmental conditions including the adsorbent dosage and dye concentration, as well as the solution pH and temperature, where an impressive CV removal capacity of 201.6-243.8 mg g-1 is recorded for a wide pH range of 2-10. Mechanism and kinetics involved in the adsorption process are investigated by studying the adsorption isotherms and thermodynamics. The dye adsorption of the nanocomposite material is confirmed to follow the pseudo-second-order kinetic model combined with the Langmuir isotherm model, exhibiting an excellent spontaneous and exothermic monolayer adsorption capacity of around 153 mg g-1 (for MO) for the fresh adsorbent and around 89 mg g-1 after three adsorption-regeneration cycles.

Hydrothermal Pretreatment of KOH for the Preparation of PAC and Its Adsorption on TC

The environment has been heavily contaminated with tetracycline (TC) due to its excessive use; however, activated carbon possessing well-developed pores can effectively adsorb TC. This study synthesized pinecone-derived activated carbon (PAC) with high specific surface area (1744.659 cm²/g, 1688.427 cm²/g) and high adsorption properties (840.62 mg/g, 827.33 mg/g) via hydrothermal pretreatment methods utilizing pinecones as precursors. The results showed that PAC treated with 6% KOH solution had excellent adsorption properties. It is found that the adsorption process accords with the PSO model, and a large amount of C=C in PAC provides the carrier for π-πEDA interaction. The results of characterization and the isothermal model show that TC plays a key role in the adsorption process of PAC. It is concluded that the adsorption process of TC on PAC prepared by hydrothermal pretreatment is mainly pore filling and π-πEDA interaction, which makes it a promising adsorbent for TC adsorption.