Adsorption of Procion Blue MX-R dye from aqueous solutions by lignin chemically modified with aluminium and manganese

Lignin: A valuable and promising bio-based absorbent for dye removal applications

The importance of environmental issues and the existence of humans have led to the recognition of environmental concerns as the main risk to modern life. Notably, one major concern for protecting and managing the environment and human health is the presence of dyes in wastewater. Therefore, before discharging wastewater into mainstream water, it is crucial to remove dyes. Among all lignocellulosic materials, lignin is a highly fragrant biopolymer. Its abundant availability, complex structure, and numerous functional moieties, including hydroxyl, carboxyl, and phenolic, are used in different chemicals and applications. Based on this, lignin is a very useful green material for adsorption, specifically in removing both heavy metals and organic pollutants from wastewater. This article describes the use of lignin-based adsorbents as a recent breakthrough in the removal of dye from aqueous solutions. On the other hand, the review intends to encourage readers to study both established and novel avenues in lignin-based dye removal materials.

Modified biochar prepared from Retinervus luffae fructus for dyes adsorption and aerobic sludge granulation

Retinervus luffae fructus biochar (RLFB) and ZnCl2 pretreated Retinervus luffae fructus biochar (ZRLFB) were prepared by pyrolysis. The as-prepared biochar was investigated for its applicability as a dye adsorber using sunset yellow (SY) and basic red 46 (BR46) dyes. Additionally, ZRLFB was used for the experimental cultivation of granular sludge. The results indicated that the adsorption effect of ZRLFB on the two dyes was higher than RLFB. The adsorption of RLFB to SY was related to the Langmuir and Freundlich models, whereas the adsorption of RLFB-BR46, ZRLFB-SY, and ZRLFB-BR46 was more in line with the Langmuir model. The adsorption process of dyes on two kinds of biochars can be described using pseudo-second-order mechanisms. The maximum adsorption capacity obtained was 1.9586 (RLFB-SY), 6.1286 (RLFB-BR46), 49.2611 (ZRLFB-SY), and 181.4882 mg g^-1 (RLFB-BR46). The result of the SBR operation showed that ZRLFB can potentially be applied as the core of aerobic granular sludge.

Mixed micellar solubilization for procion blue MxR entrapment and optimization of necessary parameters for micellar enhanced ultrafiltration

In this study, micellar enhanced ultrafiltration, MEUF, being an active methodology, has been employed to remove Procion Blue MxR (PBM) from synthetic effluent. MEUF is being applied to reduce the toxicity level of aqueous system using the micellar media of cationic surfactants i.e. Cetyl trimethylammonium bromide (CTAB) and cetylpyridinium chloride (CPC). Subsequently, the effect of addition of nonionic surfactant, Triton X-100 (TX-100), on solubilizing power of cationic surfactants is investigated. The values of partition coefficient and free energy of partition reflect the extent of interaction of the dye with the surfactants. Initially molecules of pollutants i.e. dye form ion pairs with ionic surfactants and, later on, the same is incorporated within micelle. Maximum value of free energy of partition ΔG_p has been found to be -55.49 kJmol^-1 and -50.43 kJmol in the presence of CPC and CTAB, respectively. The size of pollutant, thus, increases and, consequently, can be easily filtered. The effect of various factors i.e. concentration of surfactant, concentration of electrolyte (NaCl), transmembrane pressure, revolutions per minute (RPM) and pH, have been investigated to find the optimum conditions for maximum removal of PBM from aqueous system. The efficiency of MEUF has been assessed by calculating the values of rejection percentage and permeate flux. Both the surfactants were observed as strong candidates for PBM encapsulation but overall, maximum rejection percentage (R%) of 96.90% was attained by CPC.

Synthesis of high surface area mesoporous ZnCl2–activated cocoa (Theobroma cacao L) leaves biochar derived via pyrolysis for crystal violet dye removal

Chemically activated cocoa leaves biochar (CLB) was successfully prepared from fallen cocoa leaves (CLs) via ZnCl₂–activation and pyrolysis at 700 °C for sequestration of toxic crystal violet (CV) dye from aqueous solution. CLs and CLB were characterized using elemental analysis (CHN/O), Brunauer-Emmett-Teller method (BET), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR), X-ray diffraction (XRD) spectroscopy and scanning electron microscopy (SEM). The optimum conditions for effective removal of CV dye from aqueous solution (75.67% for CLs and 99.87% for CLB) were pH 9, initial CV dye concentration 100 mg/L, adsorbent (CLs/CLB) dose 0.4 g/L, contact time 160 min and temperature 300 K. Modified Ritchie second order best described kinetic and Liu model described equilibrium adsorption. CLs and CLB with maximum adsorption capacities 190.70 and 253.3 mg/g respectively, compete favorably with adsorbents used for removal of CV dye from wastewater in the literature. The high BET surface area (957.02 m²/g) and mean pore diameter (7.21 nm) were indicators of better adsorption efficiency of CLB. CLs showed adsorption to proceed towards endothermic process, while it was exothermic process for CLB. This study established the suitability of cocoa leaves as sustainable and environmental friendly precursor for preparation of adsorbent for the treatment of dye-containing wastewater.

Preparation, characterization, and application of a homemade graphene for the removal of Congo red from aqueous solutions

Ethylene diaminetetraacetic acid (EDTA)-functionalized graphene was synthesized from Nigerian coal using a chemical exfoliation method and the graphene was applied for the removal of Congo red dye from aqueous solutions. The synthesized coal graphene and the raw coal were characterized using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) spectroscopy, scanning electron microscopy (SEM)-energy-dispersive X-ray (EDX) spectroscopy, measurement of pHpzc (pH of point of zero charge), and Boehm titrations. The SEM data revealed surface roughness which is enhanced in the prepared graphene while the EDX revealed an increase in carbon content, the main constituent of graphene, from about 26% in the raw coal to about 80% in the prepared graphene. Various adsorption variables, such as pH, contact time, concentration of Congo red, and temperature, were varied for the removal of the dye using raw coal and the synthesized coal graphene. The Liu isotherm gave the best fit of the equilibrium data than the Langmuir, Freundlich, and Dubinin-Radushkevich models. The maximum adsorption capacities of the raw coal and synthesized coal graphene at 25°C are 109.1 mg/g and 129.0 mg/g, respectively. The Avrami fractional-order kinetic model was the best model for description of the kinetic data. The model had the lowest values of standard deviation than the pseudo-first-order and pseudo-second-order models. The adsorption process of the two materials occurred via two stages as proved by intraparticle diffusion model. The adsorption process of the Congo red removal was spontaneous, feasible, and endothermic. The study conclusively revealed the graphene nanomaterial to be a viable adsorbent for textile wastewater treatment.

Development of functional lignin-based spherical particles for the removal of vanadium(V) from an aqueous system

A new type of functional lignin-based spherical particles (L-CTAB) prepared with the use of hexadecyltrimethylammonium bromide (CTAB) was applied as an effective biosorbent for removing vanadium(V) ions. The porous structure, characteristic functional groups, electrokinetic stability, morphology and size of the L-CTAB particles were examined. The conditions of removal were also investigated, including pH (2-12), sorbent mass (0.1-0.5 g), concentration (10-100 mg/dm3), phase contact time (1-240 min) and temperature (293-333 K). At pH 5.0 the maximum sorption percentage (%S) of V(V) was 45%, while at pH 2.0 it was 32%. The maximum sorption capacity of V(V) for L-CTAB was found to be 10.79 mg/g. The kinetic data indicate that the sorption followed the pseudo-second-order and film diffusion models. Sorption equilibrium for V(V) ions removal by L-CTAB was reached after 60 min at the initial concentrations 10 and 50 mg/dm³. It has been shown that the adsorption of V(V) ions on the surface of L-CTAB is a heterogeneous, endothermic and spontaneous reaction, as evidenced by the calculated values of thermodynamic parameters - free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) - for the tested systems at different temperatures. HCl solutions, used as an L-CTAB regeneration agent, quantitatively eluted V(V) ions.

Facile fabrication and characterization of kraft lignin@Fe3O4 nanocomposites using pH driven precipitation: Effects on increasing lignin content

This work offers a facile fabrication method for lignin nanocomposites through the assembly of kraft lignin onto magnetic nanoparticles (Fe3O4) based on pH-driven precipitation, without needing organic solvents or lignin functionalization. Kraft lignin@Fe3O4 multicore nanocomposites fabrication proceeded using a simple, pH-driven precipitation technique. An alkaline solution for kraft lignin (pH 12) was rapidly injected into an aqueous-based Fe3O4 nanoparticle colloidal suspension (pH 7) under constant mixing conditions, allowing the fabrication of lignin magnetic nanocomposites. The effects of increasing lignin to initial Fe3O4 mass content (g/g), increasing in ratio from 1:1 to 20:1, are discussed with a complete chemical, structural, and morphological characterization. Results showed that nanocomposites fabricated above 5:1 lignin:Fe3O4 had the highest lignin coverage and content (>20%), possessed superparamagnetic properties (Ms ≈ 45,000 A·m2/kg2); had a negative surface charge (-30 mV), and formed multicore nanostructures (DH ≈ 150 nm). The multicore lignin@Fe3O4 nanocomposites allowed rapid magnetically induced separations from suspension. After 5 min exposure to a rare-earth neodymium magnet (1.27 mm × 1.27 mm × 5.08 mm), lignin@Fe3O4 nanocomposites exhibited a maximum methylene blue removal efficiency of 74.1% ± 7.1%. These nanocomposites have potential in magnetically induced separations to remove organic dyes, heavy metals, or other lignin adsorbates.

Factors Determining the Removal Efficiency of Procion MX in Waters Using Titanate Nanotubes Catalyzed by UV Irradiation

The treatment of wastewater from the textile industry containing organic dyes faces many challenges since these compounds resist the biodegradation process in conventional treatment units. Among the physicochemical processes, photocatalysis is considered a facile, cheap, and environmental-friendly technology for treating persistent organic pollutants in waters at low concentrations. This study investigated several physicochemical factors determining the photocatalytic activity of titanate nanotubes (TNTs) to remove Procion MX 032 (PMX), an azo dye, in waters. Degradation of PMX by photocatalytic oxidation process at room temperature (30°C) was set up with the UV irradiation in the presence of different types of photocatalyst such as ST-01 (100% anatase), industrial TiO2, TNTs calcined at 120°C and 500°C. Effect of reaction time, catalyst amount, pH, light wavelength and intensity, and oxidants was investigated. Consequently, TNTs calcined at 500°C provided the highest removal efficiency. The photocatalytic oxidation of PMX by TNT calcined at 500°C was affected by pH variation, getting the highest removal at pH of 8, and inhibited with the presence of H2O2 and O2. Particularly, the PMX degradation using titanate nanotubes was optimized under the UV-A intensity of 100 W/m2. The dye was degraded by more than 95% at the TNTs concentration of 75 mg/L and pH 8.0 after 90 min. The results suggest that photocatalysis using TNTs can be a simple but efficient treatment method to remove PMX and potentially be applied for the treatment of wastewaters containing dyes.

Promoting adsorption of organic pollutants via tailoring surface physicochemical properties of biomass-derived carbon-attapulgite

Biomass-derived carbon-attapulgite adsorbent was developed for organic pollutants removal. All the batch assays were performed to evaluate the effects of organic components, contact time, and initial concentration of organic pollutants on the adsorption performance of the as-prepared adsorbent. The samples were characterized via Brunauer-Emmett-Teller (BET), Fourier transform infrared (FTIR), X-ray diffractometer (XRD), and scanning electron microscopy (SEM). The results demonstrated that the acid-treated carbon-attapulgite adsorbent (H-ATP/BC) showed a large specific surface area (237 m² g^-1) and possessed abundant oxygen-containing functional groups and silicon-oxygen bonds (i.e., O-Si-O and O-Si), which provided more active sites and conduced to the adhesive of organic pollutants. Both physical adsorption and chemical adsorption were involved in the adsorption process, and competitive adsorption occurred when two or more target pollutants coexist. Especially, phenol and/or aniline with an aromatic ring were much more likely to adhere to the H-ATP/BC surface than pyridine, and the selectivity order of H-ATP/BC for these pollutants was phenol > aniline > pyridine. From the model fitting, it was observed that the adsorption data could be described well by a pseudo-second-order model and Freundlich isotherms. The theoretical maximum phenol, aniline, and pyridine adsorption capacities of the H-ATP/BC were 14.31 mg g^-1, 15.21 mg g^-1, and 20.74 mg g^-1, respectively. Comparison among the commercial adsorbents price also illustrated that H-ATP/BC could be a promising material for efficient treatment of organic pollutants.Graphical abstract.

Lignin-derived (nano)materials for environmental pollution remediation: Current challenges and future perspectives

The supply of affordable drinking and sufficiently clean water for human consumption is one of the world's foremost environmental problems and a large number of scientific research works are addressing this issue Various hazardous/toxic environmental contaminants in water bodies, both inorganic and organic (specifically heavy metals and dyes), have become a serious global problem. Nowadays, extensive efforts have been made to search for novel, cost effective and practical biosorbents derived from biomass resources with special attention to value added, biomass-based renewable materials. Lignin and (nano)material adorned lignin derived entities can proficiently and cost effectively remove organic/inorganic contaminants from aqueous media. As low cost of preparation is crucial for their wide applications in water/wastewater treatment (particularly industrial water), future investigations must be devoted to refining and processing the economic viability of low cost, green lignin-derived (nano)materials. Production of functionalized lignin, lignin supported metal/metal oxide nanocomposites or hydrogels is one of the effective approaches in (nano)technology. This review outlines recent research progresses, trends/challenges and future prospects about lignin-derived (nano)materials and their sustainable applications in wastewater treatment/purification, specifically focusing on adsorption and/or catalytic reduction/(photo)degradation of a variety of pollutants.

Novel Mesoporous Lignin-Calcium for Efficiently Scavenging Cationic Dyes from Dyestuff Effluent

A novel adsorbent lignin-calcium was fabricated by a simple flocculation-sedimentation approach to remove methylene blue. The structure and morphology of the well-prepared sample were analyzed by multiple characterization methods. Lignin-calcium microspheres demonstrated a mesoporous and inserted layer structure with a coarse surface. Methylene blue (MB) adsorption by lignin-calcium complied with the Langmuir model, showing a maximum adsorption amount of 803.9 mg/g, exceeding that reported in the literature by 3-22-fold. The adsorption kinetics matched the pseudo-second-order model well. The pore volume diffusion model was technically applied to evaluate the mass transfer mechanisms. The effective pore volume diffusion coefficient was 6.28 × 10^-12 m²/s. Furthermore, lignin-calcium exhibited excellent adsorbability for methylene blue across a pH range from 3 to 11 and could be regenerated by hydrochloric acid with an elution efficiency of 62.44%. Multiple mechanisms may support the adsorption. Altogether, the tailor-made lignin-calcium is promising as an efficient and sustainable adsorbent for scavenging cationic dyes from dyestuff effluent.

Facile synthesis of manganese oxide modified lignin nanocomposites from lignocellulosic biorefinery wastes for dye removal

In this study, a facile method to prepare MnO₂ nanodots modified lignin nanocomposite (MnO₂@LNP) was developed for efficient dye removal. The MnO₂@LNP displayed hierarchical spherical nanostructures, where the MnO₂ nanodots were evenly dispersed within the lignin nanosphere. Compared with lignin nanoparticles, the as-prepared MnO₂@LNP exhibits higher surface area and can be separated after adsorption. It showed excellent adsorption capacity (806 mg/g) towards a typical cationic dye, methylene blue (MB), at a fast removal rate, where more than 80% of adsorption capacity was reached within 5 min at room temperature. The high adsorption capacity was contributed by the high surface area and negative charge on the adsorbent. The adsorption process is pH-responsive and exothermic, and the spent adsorbent can be reused for at least five cycles. This study displayed an efficient method to prepare MnO₂@LNP for the high-value utilization of lignin-derived from lignocellulosic biorefinery.

Upgrading of agro-industrial green biomass residues from chocolate industry for adsorption process: diffusion and mechanistic insights

In the last decades, the world suffers from the wastes those results from unprecedented growth in the food industry. This context investigated the characteristics and suitability of utilizing cocoa shell (CS), an agro-industrial residual biomass waste from the chocolate industry, without any chemical and/or physical treatment. It is an abundant, low-cost, and green adsorbent that can be utilized for the effective removal of basic blue (BB41) as an example of cationic dye from aqueous solutions. The CS showed high adsorption potential (90.04%) with the mild operating condition, 45 min adsorption time, pH 6, CS dose 4 g/L, BB41 concentration 10 mg/L, stirring speed 400 rpm at 295 K. The kinetic, equilibrium, isotherms and mechanism studies revealed that the BB41 adsorption onto CS was attained mainly by electrostatic interaction, π-π stacking interaction, hydrogen bonding, covalent bond, and physical mechanisms. Besides, the organic functional groups played an important role during the adsorption process. The thermodynamic parameters suggested that the adsorption of BB41 dye was the non-spontaneous endothermic process with an activation energy 18.28 kJ/mol. From the industrial point of view, this work offers an economical push in waste management and also a green approach for the effective removal of toxic dyes from textile wastewater.

Evaluation of efficiency and selectivity in the sorption process assisted by chemometric approaches: Removal of emerging contaminants from water

This paper describes, by the first time, a chemometric approach that combines a simple set of the UV-Vis spectra and partial least square regression (PLSR) for measuring the removal of five pharmaceuticals present in simulated hospital effluents by sorption using activated carbon. The use of multivariate calibration allowed the quantification of the remaining concentrations of the studied drugs present in a complex mixture with high accuracy, avoiding the need for the use of sophisticated methodologies based on chromatography. Isothermal sorption studies were performed on single-component solutions containing amoxicillin, paracetamol, propranolol, sodium diclofenac, or tetracycline as well as on a solution containing a mixture of all these 5 compounds. The isotherm data obtained were fitted to the Langmuir, Freundlich and Liu models. It was observed that for each pharmaceutical, the maximum sorption capacity of the activated carbon was higher for the single component than in the mixture. It was observed that the removal of paracetamol, propranolol, and tetracycline, the removal was complete (100%) and for amoxicillin and sodium diclofenac it was at least 92.71 ± 3.15% and 91.82 ± 0.95% respectively, indicating that the avocado seed activated carbon is an adsorbent with high sorption capacity that can remove five pharmaceuticals from simulated hospital effluents.

Novel magnetic amine functionalized carbon nanotube/metal-organic framework nanocomposites: From green ultrasound-assisted synthesis to detailed selective pollutant removal modelling from binary systems

Herein, magnetic amine functionalized carbon nanotube (NH₂-CNT/Fe₂O₃)-zeolitic imidazolate framework-8 (ZIF-8) nanocomposites (NH₂-CNT/Fe₂O₃/ZIF-8: NCFZ) with different amounts of NH₂-CNT/Fe₂O₃ (5, 10, and 15 wt% denoted as NCFZ-5, NCFZ-10, and NCFZ-15) were synthesized. The synthesized nanomaterials including ZIF-8, Fe₂O₃, CNT/Fe₂O₃, NH₂-CNT/Fe₂O₃, CNT/Fe₂O₃/ZIF-8, NCFZ-5, NCFZ-10, and NCFZ-15 were characterized using BET, TEM, XRD, SEM, FTIR, VSM and zeta potential. The synthesized nanomaterials were applied for selective removing cationic dyes (MG: Malachite Green and RhB: Rhodamine B) from a binary system. Response surface methodology (RSM) and artificial neural networks (ANN) were used for optimizing dye removal. The BET data showed that the surface area of nanocomposite (NH₂-CNT/Fe₂O₃/ZIF-8: 1659 m²/g) was higher than that of pure ZIF-8 (1485 m²/g). Contaminant removal obeyed the Freundlich isotherm and pseudo-second order kinetic models. The optimum adsorption condition predicted by RSM was pH = 6, dye concentration = 25 mg/L, Dosage = 0.004 g and at time = 145 min. The outputs of ANN model well overlapped with the experimental data. The binary system dye removal data indicated the synthesized nanocomposite with recycling and regeneration ability could be used for treating wastewater.

Kinetic, equilibrium, and thermodynamic studies on the adsorption of ciprofloxacin by activated carbon produced from Jerivá (Syagrus romanzoffiana)

High specific surface area activated carbon prepared from endocarp of Jerivá (Syagrus romanzoffiana) (ACJ) was used for ciprofloxacin (CIP) antibiotic removal from aqueous effluents. The activated carbon (AC) was characterized via scanning electron microscope, Fourier transform infrared spectroscopy, N₂ adsorption/desorption, and pH value at the zero-charge point. Avrami kinetic model was the one that best fit the experimental results in comparison to the pseudo-first-order and pseudo-second-order kinetic models. The equilibrium data obeyed the Liu isotherm equation, showing a maximum adsorption capacity of 335.8 mg g^-1 at 40 °C. The calculated thermodynamic parameters indicate that the adsorption of CIP was spontaneous and endothermic at all studied temperatures. Also, the free enthalpy changes (∆H° = 3.34 kJ mol^-1) suggested physical adsorption between CIP and ACJ. Simulated effluents were utilized to check the potential of the ACJ for wastewater purification. The highly efficient features enable the activated carbon prepared from endocarp of Jerivá, an attractive carbon adsorbent, to remove ciprofloxacin from wastewaters.

Lignin materials for adsorption: Current trend, perspectives and opportunities

Lignin is a highly aromatic low value biomass residue, which can be utilized for chemicals, fuels and materials production. In recent years significant attention has focused on adsorbent materials from lignin. However, only 5% of available lignin is exploited worldwide, thus significant opportunities still exist for materials development. This review summarizes recent research advances in lignin-based adsorbents, with a particular emphasis on lignin, its modification and carbon materials derived from this abundant feedstock. Lignin derived activated carbons have been utilized for air pollutant adsorption (e.g. CO₂, SO₂ and H₂S), while modified lignin materials have been developed for the removal of organic dyes and organics (like methylene blue, Procion Blue MX-R and phenols), heavy metals (such as Cu, Zn, Pb and Cd), or recovery of noble metals (e.g., Pd, Au and Pt). Future perspectives highlight how green chemistry approaches for developing lignin adsorbents can generate added value processes.

A critical review on recent advancements of the removal of reactive dyes from dyehouse effluent by ion-exchange adsorbents

The effluent discharged by the textile dyehouses has a seriously detrimental effect on the aquatic environment. Some dyestuffs produce toxic decomposition products and the metal complex dyes release toxic heavy metals to watercourses. Of the dyes used in the textile industry, effluents containing reactive dyes are the most difficult to treat because of their high water-solubility and poor absorption into the fibers. A range of treatments has been investigated for the decolorization of textile effluent and the adsorption seems to be one of the cheapest, effective and convenient treatments. In this review, the adsorbents investigated in the last decade for the treatment of textile effluent containing reactive dyes including modified clays, biomasses, chitin and its derivatives, and magnetic ion-exchanging particles have been critically reviewed and their reactive dye binding capacities have been compiled and compared. Moreover, the dye binding mechanism, dye sorption isotherm models and also the merits/demerits of various adsorbents are discussed. This review also includes the current challenges and the future directions for the development of adsorbents that meet these challenges. The adsorption capacities of adsorbents depend on various factors, such as the chemical structures of dyes, the ionic property, surface area, porosity of the adsorbents, and the operating conditions. It is evident from the literature survey that decolorization by the adsorption shows a great promise for the removal of color from dyehouse effluent. If biomasses want to compete with the established ion-exchange resins and activated carbon, their dye binding capacity will need to be substantially improved.

Production of Flocculants, Adsorbents, and Dispersants from Lignin

Currently, lignin is mainly produced in pulping processes, but it is considered as an under-utilized chemical since it is being mainly used as a fuel source. Lignin contains many hydroxyl groups that can participate in chemical reactions to produce value-added products. Flocculants, adsorbents, and dispersants have a wide range of applications in industry, but they are mainly oil-based chemicals and expensive. This paper reviews the pathways to produce water soluble lignin-based flocculants, adsorbents, and dispersants. It provides information on the recent progress in the possible use of these lignin-based flocculants, adsorbents, and dispersants. It also critically discusses the advantages and disadvantages of various approaches to produce such products. The challenges present in the production of lignin-based flocculants, adsorbents, and dispersants and possible scenarios to overcome these challenges for commercial use of these products in industry are discussed.

Bio-Based Cellulose Acetate Films Reinforced with Lignin and Glycerol

Two sets of four cellulose acetate (degree of substitution = 2.2) were incorporated with lignin extracted from the macaúba endocarp, before and after being chemically modified to sodium carboxymethyl-lignin and aluminum carboxymethyl-lignin, respectively. The eight membranes were prepared by the casting method after dissolution in acetone and embedded with lignins (0.1% w/w), one without modification (CAc-Lig) and two chemically modified (CAc-CMLNa) and (CAc-CMLAl), compared to membranes of pure acetate (CAc). In group II, in the four membranes prepared, glycerol was added (10% w/w) as a plasticizer. The membranes were characterized by a number of techniques: thermal (differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA)), morphological (scanning electron microscope (SEM) and atomic force microscopy (AFM)), structural (X-ray powder diffraction (XRD)), hydrophobic (contact angle and water vapor permeability), and thermomechanical (dynamic thermal mechanical analysis and tensile tests). The results show that despite some incompatibility with the cellulose acetate, the incorporation of the lignin in a concentration of 0.1% w/w acts as a reinforcement in the membrane, greatly increasing the tension rupture of the material. The presence of glycerol in a concentration of 10% w/w also acts as a reinforcement in all membranes, in addition to increasing the tension rupture. In this study, glycerol and acetate both increased the compatibility of the membranes.

One-Step Fabrication of Dual Responsive Lignin Coated Fe₃O₄ Nanoparticles for Efficient Removal of Cationic and Anionic Dyes

A new, simple one-step approach has been developed to synthesize lignin and lignin amine coated Fe₃O₄ nanoparticles. These nanoparticles (lignin magnetic nanoparticles (LMNPs) and lignin amine magnetic nanoparticles (LAMNPs)) are found to possess not only magnetic response but also pH-dependent adsorption behavior. Results show that the combination of lignin with nanoparticles increased the adsorption capacities 2-5 times higher than other traditional single lignin based adsorbents (211.42 mg/g for methylene blue (MB) by LMNPs and 176.49 mg/g for acid scarlet GR (AS-GR) by LAMNPs). Meanwhile, by simply adjusting the pH, the dye-loaded adsorbents can be regenerated to recycle both adsorbents and dyes with a desorption efficiency up to 90%. Mechanistic study shows that dye structure and surface charges of adsorbents play the most important part in adsorption where dyes interact with the adsorbent surface via π-π stacking and electrostatic attraction interactions. The efficient fabrication method, eco-friendly reactant, quick magnetic separation, high adsorption and desorption efficiency suggest this novel type of nano-adsorbents to be promising materials for efficient dye pollutant removal and recovery.

Study on adsorption of rhodamine B onto Beta zeolites by tuning SiO2/Al2O3 ratio

The exploration of the relationship between zeolite composition and adsorption performance favored to facilitate its better application in removal of the hazardous substances from water. The adsorption capacity of rhodamine B (RB) onto Beta zeolite from aqueous solution was reported. The relationship between SiO₂/Al₂O₃ ratio and adsorption capacity of Beta zeolite for RB was explored. The structure and physical properties of Beta zeolites with various SiO₂/Al₂O₃ ratios were determined by XRD, FTIR, TEM, BET, UV-vis and so on characterizations. The adsorption behavior of rhodamine B onto Beta zeolite matched to Langmuir adsorption isotherm and more suitable description for the adsorption kinetics was a pseudo-second-order reaction model. The maximum adsorption capacity of the as-prepared Beta zeolite with SiO₂/Al₂O₃ = 18.4 was up to 27.97mg/g.

Surface modified composite nanofibers for the removal of indigo carmine dye from polluted water

Surface coated magnetite nanoparticles (Fe₃O₄ NPs) with 3-mercaptopropionic acid were immobilized on amidoximated polyacrilonitrile (APAN) nanofibers using electrospinning followed by crosslinking. The prepared composite nanofibers were characterized with Scanning Electron Microscopy (SEM), and Fourier Transform Infrared analysis (FTIR). The composite nanofiber was evaluated for the removal of indigo carmine dye from aqueous solutions. The effects of contact time, initial dye concentration, solution pH and adsorption equilibrium isotherms were studied. The adsorption of indigo carmine was found to be greatly affected by solution pH. The maximum loading capacity was determined to be 154.5 mg g⁻¹ at pH = 5. The experimental kinetic data were fitted well using a pseudo-first order model. The adsorption isotherm studies showed that the adsorption of indigo carmine fits well with the Langmuir model. The reuse of the composite nanofiber was also investigated in which more than 90% of indigo carmine was recovered in 5 min. The results of stability studies showed that the adsorption efficiency can remain almost constant (90%) after five consecutive adsorption/desorption cycles.

Surface coated magnetite nanoparticles (Fe₃O₄ NPs) with 3-mercaptopropionic acid were immobilized on amidoximated polyacrilonitrile (APAN) nanofibers using electrospinning followed by crosslinking.

Preparation and characterization of amine-functionalized sugarcane bagasse for CO2 capture

A low-cost solid amine adsorbent for CO2 capture was prepared by using sugarcane bagasse (SB), a dominant agro-industrial residue in the sugar and alcohol industry as raw materials. In this preparation process, acrylamide was grafted on SB, and the grafted fiber was then aminated with different type of amine reagents to introduce primary and secondary amine groups onto the surface of SB fibers. The graft and amination conditions were optimized. The prepared solid amine adsorbent showed remarkable CO2 adsorption capacity and the adsorption capacity of the solid amine adsorbent could reach 5.01 mmol CO2/g at room temperature. The comparison of adsorption capacities of amine fibers aminated with various amination agents demonstrated that fibers aminated with triethylenetetramine would obtain higher adsorption capacities and higher amine efficiency. These adsorbents also showed good regeneration performance, the regenerated adsorbent could maintain almost the same adsorption capacity for CO2 after 10 recycles.

Sisal fiber-based solid amine adsorbent and its kinetic adsorption behaviors for CO2

A sisal-based solid amine adsorbent was prepared by grafting acrylamide and then aminating with amine agents. Remarkable CO₂ adsorption capacity (4.20 mmol g⁻¹) was achieved due to unique texture of vegetable and plentiful amine groups.

Competitive adsorption of three phenolic compounds to hydrophilic urea-formaldehyde macroporous foams derived from lignin-based Pickering HIPEs template

Hydrophilic urea-formaldehyde macroporous foams (UFMF) were simply synthesized by templating oil-in-water Pickering high internal phase emulsions (HIPEs) solely stabilized by lignin particles.

Synthesis, characterization of nitrogen-doped mesoporous carbon spheres and adsorption performance

Nitrogen-doped mesoporous carbon spheres (NMCS) were prepared by a nanocasting route using benzoxazine resins as the precursor of nitrogen and carbon, and ordered mesoporous silica spheres as the hard template to remove methyl orange (MO).

Microwave-assisted activated carbon from cocoa shell as adsorbent for removal of sodium diclofenac and nimesulide from aqueous effluents

Microwave-induced chemical activation process was used to prepare an activated carbon from cocoa shell for efficient removal of two anti-inflammatories, sodium diclofenac (DFC) and nimesulide (NM), from aqueous solutions. A paste was obtained from a mixture of cocoa shell and inorganic components; with a ratio of inorganic: organic of 1 (CSC-1.0). The mixture was pyrolyzed in a microwave oven in less than 10 min. The CSC-1.0 was acidified with a 6 mol L(-1) HCl under reflux to produce MWCS-1.0. The CSC-1.0 and MWCS-1.0 were characterized using FTIR, SEM, N2 adsorption/desorption curves, X-ray diffraction, and point of zero charge (pHpzc). Experimental variables such as initial pH of the adsorbate solutions and contact time were optimized for adsorptive characteristics of MWCS-1.0. The optimum pH for removal of anti-inflammatories ranged between 7.0 and 8.0. The kinetic of adsorption was investigated using general order, pseudo first-order and pseu do-second order kinetic models. The maximum amounts of DCF and NM adsorbed onto MWCS-1.0 at 25 °C are 63.47 and 74.81 mg g(-1), respectively. The adsorbent was tested on two simulated hospital effluents. MWCS-1.0 is capable of efficient removal of DCF and NM from a medium that contains high sugar and salt concentrations.