Amines modified fibers obtained from natural Populus tremula and their rapid biosorption of Acid Blue 25

Chemical modification of microcrystalline cellulose with polyethyleneimine and hydrazine: Characterization and evaluation of its adsorption power toward anionic dyes

Functionalization and various applications of biomaterials have progressively gained a major interest due to the cost-effectiveness, renewability, and biodegradability of these substrates. The current work focalized on the functionalization of microcrystalline cellulose with polyethyleneimine solution (3 %, 5 %, and 10 %) and hydrazine sulfate salt (1:1, 1:2, 2:1) using an impregnation method. Untreated and treated samples were characterized using FT-IR, SEM, XRD, TGA, and DTA analyses. The crystallinity index values for control microcrystalline cellulose, cellulose-polyethyleneimine, and cellulose-hydrazine were 57.13.8 %, 57.29 %, and 52.62 %, respectively. Cellulose-polyethyleneimine (5 %) and cellulose-hydrazine (1:1) displayed the highest adsorption capacities for calmagite (an anionic dye). At equilibrium, the maximum adsorption capacities for calmagite achieved 104 mg/g for cellulose-polyethyleneimine (5 %), 45 mg/g for cellulose-hydrazine (1:1), and only 12.4 mg/g for untreated cellulose. Adsorption kinetics complied well with the pseudo-second-order kinetic model. The adsorption isotherm fitted well with the Langmuir isotherm. Overall, the functionalized cellulosic samples could be considered potential materials for the treatment of contaminated waters.

Characterization and application of ligno-cellulosic fibers derived from Robinia Pseudoacacia for the bio-sorption of methylene blue from water

Ligno-cellulosic biomasses had been recognized for their potential use to produce chemicals and biomaterials. The current study focused on the use of a new cellulosic Robinia Pseudoacacia fiber and extracted lignin as adsorbents for methylene blue (a cationic dye). The biomaterials were analyzed using FT-IR spectroscopy, SEM, XRD, and TGA-DTA techniques. The surface of Robinia fibers was rough and porous. The crystallinity index (CrI) value for Robinia fibers was found to be 32%. The ability of the studied samples to remove methylene blue from water was assessed under the variation of time, pH, dye concentration, temperature, and NaCl concentration. The maximum adsorption capacity of methylene blue reached 191 mg/g for Robinia fibers and it achieved 22 mg/g for the extracted lignin (T = 20 °C, pH = 6, and time = 90 min). The adsorption data complied with the pseudo second-order kinetic model and both Langmuir and Freundlich isotherms. Based on these findings, the process suggested the occurrence of many physicochemical interactions between methylene blue molecules and the studied biomaterials. The adsorption mechanism was exothermic, non-spontaneous, and it was described by the decrease of the disorder. Adsorption results proved that Robinia fiber was an attractive candidate for the removal of cationic dyes from water.

A censorious review on the role of natural lignocellulosic fiber waste as a low-cost adsorbent for removal of diverse textile industrial pollutants

BACKGROUND

Textile industries produce fabricated colored products using toxic dyes and other harsh chemicals. It is the responsibility of the textile industries to treat and eliminate these hazardous pollutants. However, due to the growing population demand, the treatment of these hazardous effluents is ineffective and imposes the treatment cost over the end users. The release of partially treated effluents in the environment may cause a severe threat to the ecology and its biota. The critical objective is to treat textile effluents efficiently using agricultural natural fiber waste. Generation of agricultural lignocellulosic fibrous waste increases every year due to growing population demand. Its use in the modern world is limited due to synthetic products. An alternative has enumerated to avoid wastage of fibrous resources and its clean disposal.

OBJECTIVE

The main objective of this review paper discussed the feasibility of lignocellulosic fibers and other lignocellulosic materials as natural low-cost adsorbent.

METHODS

The literature study was performed using Web of Science and Scopus indexed journals. The main factors considered to increase the adsorption ability, including the types of lignocellulosic surface modification techniques were searched with utmost importance for quality results. Intending to summarize the literature survey and provide persuasive content, systematic review process was considered for this novel article.

RESULTS

Out of 230 valuable publications, 159 published articles were considered for the present study until March 2022. The articles surplus with factors affecting adsorption (pH, adsorption dosage, surface area, temperature, initial concentration, contact time, physical and chemical properties of pollutants) and surface modification techniques (physical, chemical, and biological) were considered for this manuscript.

CONCLUSION

Overall, the physical and chemical modification methods are widely used instead of biological methods due to various factors as discussed briefly. Furthermore, the finding of this article supports the fact that the fibrous by-product resources are wasted in various occasions due to the modern lifestyle. Even though there is evidential possibility to implement the low-cost adsorbents, the industries limit their application prospects due to existing technology and financial compromises.

Recent advances in the removal of dyes from wastewater using low-cost adsorbents

The presence of hazardous dyes in wastewater cause disastrous effects on living organisms and the environment. The conventional technologies for the remediation of dyes from water have several bottlenecks such as high cost and complex operation. This review aims to present a comprehensive outlook of various bio-sorbents that are identified and successfully employed for the removal of dyes from aqueous environments. The effect of physicochemical characteristics of adsorbents such as surface functional groups, pore size distribution and surface areas are critically evaluated. The adsorption potential at different experimental conditions of diverse bio-sorbents has been also explored and the influence of certain key parameters like solution pH, temperature, concentration of dyes, dosage of bio-sorbent and agitation speed is carefully evaluated. The mechanism of dyes adsorption, regeneration potential of the employed bio-sorbents and their comparison with other commercial adsorbents are discussed. The cost comparison of different adsorbents and key technological challenges are highlighted followed by the recommendations for future research.

Fabrication and Properties of Tree-Branched Cellulose Nanofibers (CNFs) via Acid Hydrolysis Assisted with Pre-Disintegration Treatment

In this paper, the novel morphology of cellulose nanofibers (CNFs) with a unique tree-branched structure was discovered by using acid hydrolysis assisted with pre-disintegration treatment from wood pulps. For comparison, the pulps derived from both softwood and hardwood were utilized to extract nanocellulose in order to validate the feasibility of proposed material fabrication technique. The morphology, crystalline structures, chemical structures, and thermal stability of nanocellulose were characterized by means of transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FTIR), as well as thermogravimetric analysis (TGA). Prior to acid hydrolysis, softwood and hardwood pulps underwent the disintegration treatment in the fiber dissociator. It has been found that nanocellulose derived from disintegrated pulps possesses much longer fiber length (approximately 5-6 μm) and more evident tree-branched structures along with lower degree of crystallinity when compared with those untreated counterparts. The maximum mass loss rate of CNFs takes place at the temperature level of approximately 225 °C, and appears to be higher than that of cellulose nanowhiskers (CNWs), which might be attributed to an induced impact of amorphous content. On the other hand, disintegration treatment is quite beneficial to the enhancement of tensile strength of nanocellulose films. This study elaborates a new route of material fabrication toward the development of well-tailored tree-branched CNFs in order to broaden the potential widespread applications of nanocellulose with diverse morphological structures.

Evaluation of Original and Enzyme-Modified Fique Fibers as an Azo Dye Biosorbent Material

As natural fibers, low-cost biosorbents have proven to be an effective and clean tool to remove textile dyes from wastewater. In this research, the Reactive Black 5 removal ability of original and enzyme-modified natural fibers were assessed. A fiber extracted from a Colombian fique plant (Furcraea sp.) was employed. The effects of fique fiber protonation with different solvents and dye solution pH on RB5 removal were evaluated. The biosorbent chemical composition was modified using the commercial enzymes pectinase, ligninase, and xylanase. The point of zero charge (PZC) of the original and modified material was measured, and the dye removal capacity of the three enzyme-modified fibers was determined. Fiber protonation with 0.1 M HCl and a dye solution with pH of 2.4 increased the RB5 elimination to 49.1%. The change in the fiber chemical composition led to a reduction in the PZC from 5.5 to a 4.7–4.9 range. Pectinase-pretreated fique fibers presented the highest dye removal of 66.29%, representing a 36% increase in RB5 dye removal. Although the original fique fiber showed RB5 dye removal ability, its enzymatic modification changed the charge distribution on the fiber surface, improving the capture of dye molecules. Enzyme modification can be applied to obtain new functionalities for plant fibers as biosorbent materials.

Mesoporous activated carbon as a green adsorbent for the removal of heavy metals and Congo red: Characterization, adsorption kinetics, and isotherm studies

In this study, an effective and green adsorbent was prepared by the self- activation of kenaf fiber and then the kenaf-based activated carbon (KAC) was applied for the removal of lead Pb(II), copper Cu(II), and Congo red (CR) dye from an aqueous solution by the process of adsorption. The surface morphology of mesoporous adsorbent was characterized. The KAC showed good capacity of adsorption of as Pb(II), Cu(II), and anionic dye CR in very short period of agitation. The adsorbent efficiency of metal ions and dye was estimated by varying the adsorbent dose, pH, contact time, initial metals and dye concentration, and temperature. Optimum adsorption of metal ions and CR dye was observed at pH 6, and at pH 4 at 120 min, respectively. The adsorption isotherm was described by the Langmuir and Freundlich isotherm equations. The green adsorbent followed the pseudo-second-order kinetic model with correlation coefficients R² value >0.99. The increase in adsorption temperature enhanced the adsorption efficiency for both heavy metals and dye. The KAC showed no significant loss of the adsorption capacity after 3 cycles of reuse.

Synthesis and investigation on optical and electrochemical properties of 2,4-diaryl-9-chloro-5,6,7,8-tetrahydroacridines

A facile synthesis of 2,4-diaryl-9-chloro-5,6,7,8-tetrahydroacridine derivatives is reported which is based on POCl₃-mediated cyclodehydration followed by double Suzuki-Miyaura cross-coupling. The absorption and fluorescence properties of the obtained products were investigated and their HOMO/LUMO energy levels were estimated by cyclic voltammetry measurements. Besides, density functional theory calculations were carried out for further exploration of their electronic properties.

Extraction of Cellulose Polymeric Material from Populus tremula Fibers: Characterization and Application to the Adsorption of Methylene Blue and Crystal Violet

Cellulose is the most widely available biopolymer which is extensively used for several applications including textiles, composites, pharmaceutical, water treatment, etc. In this investigation, cellulose was chemically extracted from Populus tremula seed fibers. Samples were characterized using FT-IR, SEM, XRD, and TGA-DTA analyses. FT-IR spectrum of the extracted cellulose confirmed that hemicellulose and lignin were removed during alkali and bleaching treatments. SEM images showed the partially roughened surface of the fiber due to the removal of non-cellulosic elements and surface impurities during chemical modification. The crystallinity index values for untreated Populus tremula fibers and extracted cellulose were calculated to be 32.8% and 58.9%, respectively. The obvious increase in the crystallinity index for the extracted cellulose confirmed the removal of amorphous compounds present in raw populus. Alkali-treated populus fibers were more thermally stable than raw fibers. All changes observed after alkali and bleaching treatments evidenced the removal of amorphous contents and non-cellulosic components in raw populus fibers. Extracted cellulose exhibited excellent adsorption capacities of methylene blue (140.4 mg g⁻¹) and crystal violet (154 mg g⁻¹). The pseudo second order equation fitted well the kinetic data indicating a chemi-sorption process. The Freundlich model complied well with the experimental data suggesting that the adsorption of the studied dyes was multilayer.

Functionalization of cellulosic fibers with a kaolinite-TiO2 nano-hybrid composite via a solvothermal process for flame retardant applications

Eco-responsible flame retardant treatments with some resistance to washing are of considerable interest in the sale and applications of technical garments and home textiles. Thus, in the present study, a nano-hybrid composite based on kaolinite-TiO₂ was prepared and incorporated into the fibers of cotton fabric through a more sustainable route compared to existing commercial processes. SEM analyses revealed a mineral covering of the treated cotton fibers, which do not propagate flames when exposed to fire and have a self-extinguishing behavior after the heat source removal. The method proved to be efficient in obtaining a cotton product with high fireproof performance. It was observed that after functionalization, the fabric showed a thermal degradation 41% less at 800 °C, an increase in the residue formation, and a reduction of about 85% in peak heat release measured by PCFC. Some resistance to washing was noticed, and the mechanical resistance of fibers was preserved.

Biogenic synthesis of novel platinum-palladium bimetallic nanoparticles from aqueous Annona muricata leaf extract for catalytic activity

This work reports the fast and effective bio-fabrication of novel platinum-palladium bimetallic nanoparticles (Pt-Pd BNPs) along with their counterparts Pt and Pd monometallic NPs (MNPs) through aqueous Annona muricata leaf extract. The bio-fabrication of the NPs was achieved within 2 h at 100 °C and pH 7 which was established by the occurrence of dark brown color for Pt MNPs and black color for Pd MNPs and Pt-Pd BNPs. NPs were evaluated for their catalytic activity in the reduction of methyl orange (MO), rhodamine-B (rh-B), and methylene blue (MB) textile dyes in presence of sodium borohydride as a reducing agent. Pt-Pd (1:3) BNPs showed higher MO dye degradation (96.84 ± 2.05% in 50 min) followed by Pd MNPs (97.07 ± 1.46% in 60 min), Pt-Pd (3:1) BNPs (97.34 ± 1.17% in 70 min) and Pt-Pd (1:1) BNPs (98.12 ± 1.04% in 80 min). Pd MNPs showed significant catalytic activity in the reduction of rh-B dye by 97.27 ± 1.14% in 12 min followed by Pt-Pd (3:1) BNPs (96.76 ± 2.17% in 18 min), Pt-Pd (1:3) BNPs (96.53 ± 1.97% in 33 min) and Pt-Pd (1:1) BNPs (97.11 ± 2.09% in 39 min). Pt-Pd (1:3) BNPs also showed higher MB dye degradation (96.95 ± 1.57% in 40 min) followed by Pd MNPs (96.22 ± 2.36% in 55 min), Pt-Pd (3:1) BNPs (97.29 ± 1.22% in 75 min) and Pt-Pd (1:1) BNPs (96.45 ± 2.19% in 105 min). However, Pt MNPs showed no catalytic activity. Standard disc diffusion method was used to evaluate the NPs toxicity towards Escherichia coli and Staphylococcus aureus, which showed no inhibitory zones. NPs showed less toxicity compared to potassium dichromate (control) against Artemia nauplii. Among the NPs studied, Pt-Pd (1:1) BNPs showed less toxicity with 100% mortality only at 100 µg/mL concentration followed by Pt MNPs (≥ 80 µg/mL), Pt-Pd (1:3) BNPs (≥ 60 µg/mL), Pt-Pd (3:1) BNPs (≥ 60 µg/mL) and Pd MNPs (≥ 40 µg/mL) after 72 h exposure. These evaluations support the application of bio-fabricated Pt-Pd BNPs as nano-catalysts in textile dyes degradation.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-02935-0.

2,4-Bis(arylethynyl)-9-chloro-5,6,7,8-tetrahydroacridines: synthesis and photophysical properties

Acridine derivatives have attracted considerable interest in numerous areas owing to their attractive physical and chemical properties. Herein, starting from readily available anthranilic acid, an efficient synthesis of 2,4-bis(arylethynyl)-9-chloro-5,6,7,8-tetrahydroacridine derivatives was accomplished via a one-pot double Sonogashira cross-coupling method. The UV-visible absorption and emission properties of the synthesized molecules have been examined. Additionally, theoretical studies based on density functional theory (DFT/B3LYP/6-31G(d)) were carried out.

Characterization and valuable use of Calotropis gigantea seedpods as a biosorbent of methylene blue

In this work, powdered Calotropis gigantea seedpods were characterized and used as biosorbents of methylene blue dye from aqueous solution. FT-IR spectroscopy demonstrated functional groups characteristics of cellulose. Steric exclusion chromatography donated an average molecular weight of 230 kg/mol of the biopolymer. The polymolecularity index value (1.95) proved the good homogeneity of the polysaccharide. Scanning electron microscopy features displayed a homogenous morphology and porous structure. X-ray diffraction patterns showed peaks characteristics of cellulose and non-cellulose compositions. Thermogravimetric analysis/differential thermal analysis displayed exothermal decompositions at 316.9 °C and 456 °C. The maximum biosorption capacity of methylene blue was 88.36 mg/g at pH = 6, time = 60 min, and T = 21 °C. The level was comparable to some other studied agricultural wastes. The adsorption mechanism followed pseudo-second-order and Freundlich models. As it is abundant, available, low-cost, and easily recovered from solution, C. gigantea seedpods could be used as an effective biomaterial for the removal of organic pollutants from contaminated waters. Novelty statement: An abundant, available, and low-cost Calotropis gigantea seedpod was used, for the first time, as an effective biomaterial for the biosorption of organic pollutants. The biosorption level was found to be comparable to some other agricultural wastes studied previously in the literature.

Engineered Fe3 triangle for the rapid and selective removal of aromatic cationic pollutants: complexity is not a necessity

In this study, a low-cost oxo-bridged {Fe3} triangular cluster was constructed based on a benzoate ligand via slow evaporation. The cluster was thoroughly characterized by FTIR and UV-visible spectroscopy, TGA, and PXRD, and the exact structure was elucidated by single-crystal XRD. The formation of C-H⋯π and π-π interactions is responsible for the extra stability of {Fe3} clusters, which further enhances the dye adsorption property. The dye adsorption experiments performed on cationic [methylene blue (MB) and rhodamine-B (Rh-B)] as well as anionic [methyl orange (MO) and congo red (CR)] dyes revealed the ultimate selectivity of the present cluster towards the cationic ones. The {Fe3} cluster exclusively adsorbs the cationic dyes, i.e., MB and Rh-B even in the presence of anionic dyes, i.e., CR and MO. The extra stability, reusability and high efficiency of the {Fe3} molecular ensemble make it an attractive and fascinating material of importance. The kinetics analysis was evaluated employing different kinetics models. Furthermore, the plausible adsorption mechanism was also proposed, which suggests the interplay of cation-π and π-π interactions consolidating the efficient adsorption. Thus, the present work opens new doors for coordination chemists to further tune the structural features to modulate the adsorption/separation capacities of simple low-cost clusters for environmental protection for future efforts.

Comparative studies on lignin structures in normal and tension wood of Populus × euramericana cv. "74/76"

Tension wood is a type of defect of wood, however, it has some especial character and structure. In this study, cellulase lignin structures in normal and tension wood of Poplar 107 (Populus × euramericana cv. '74/76') were compared using ultraviolet (UV), Fourier transform infrared (FT-IR), Raman and magnetic resonance (NMR) spectroscopy, gel permeation chromatography (GPC) and elemental analysis. The results showed that the lignins in both normal and tension wood were dominated by syringyl units, followed by guaiacyl and p-hydroxyphenyl units. The FT-IR result presented that the relative intensity of syringyl units in normal and tension wood were 0.87 and 0.90. The contents of aliphatic hydroxyl, methoxyl, condensed phenolic hydroxyl and carboxyl of lignin in tension wood were higher than those of phenolic hydroxyl groups and β-5. The contents of β-O-4, β-β and β-1 in tension wood were similar with those in normal wood. The average per-C₉-unit formulae of the lignin in normal and tension wood of Poplar 107 were C₉H_7.21O_1.79 (OH)_{1.17_x0001_}(OCH₃)_1.55 and C₉H_7.23O_1.76(OH)_{1.25_x0001_}(OCH₃)_1.62, respectively.

Prussian blue immobilized cellulosic filter for the removal of aqueous cesium

Cesium is a typical radioisotope that has a long half-life and is dangerous and can be emitted in the event of a nuclear accident. Prussian blue (PB), which is known to effectively adsorb cesium, is difficult to separate when it is dissolved in an aqueous system. In this study, PB was immobilized on a filter type support media, cellulose filter (CF), for use as a selective material for cesium adsorption. The commercially available CF was functionalized by the addition of acrylic acid (AA) (i.e., CF-AA) to enhance the PB immobilization, which increased both PB loading and binding strength. The AA functionalization changed the major functional groups from hydroxyl to carboxylic, as confirmed by Fourier-transform infrared spectroscopy. As a result of the surface modification, the PB immobilization increased 1.5 times and reduced detachment of PB during washing. The prepared adsorbent, CF-AA-PB, was tested for its cesium adsorption capability. Cesium adsorption equilibrated within 3 h, and the maximum cesium adsorption capacity was 16.66 mg/g. The observed decrease in the solution pH during cesium adsorption inhibited the overall cesium uptake; however, this was minimized by buffering. The prepared CF-AA-PB was used as a filter material and its potential use as a countermeasure for removing radioactive cesium from a contaminated water stream was demonstrated.

Creation of Hollow Calcite Single Crystals with CQDs: Synthesis, Characterization, and Fast and Efficient Decontamination of Cd(II)

In this work, carbon quantum dots were first prepared through one-pot hydrothermal route of the propyl aldehyde and sodium hydroxide via an aldol condensation reaction, and a novel solid-phase extraction adsorbent of hollow calcite single crystals was prepared via the precipitation of metal nitrates by the CO₂ diffusion method in the presence of CQDs and further applied for excessive Cd(II) ions removal from water. The spectra and morphologies of the etched calcite were investigated by X-ray diffraction, Fourier transform infrared spectrometry, Scanning electron microscope, and Transmission electron microscopy. The results show that the CQDs etching technique successfully furnish a strategy for manufacturing interface defects onto the calcite crystal. Bath studies were done to evaluate the effects of the major parameters onto Cd(II) adsorption by the etched calcite, such as pH, contact time, and initial Cd(II) concentration. The Cd(II) adsorption onto the new adsorbent could reach a maximum adsorption amount of 66.68 mg/g at 120 min due to the abundant exterior adsorption sites on the adsorbent. The adsorption kinetics and adsorption isotherms of Cd(II) on the etched calcite were also investigated. The experimental datum showed that the adsorption kinetics and isotherms of Cd(II) on the etched calcite were well-fitted by the pseudo-second-order kinetic model and the Freundlich isotherm model respectively. The adsorption mechanisms could be primarily explained as the formation of Cd(OH)₂ and Ca_xCd_1-xCO₃ solid solution on the adsorbent surface with the help of X-ray photoelectron spectroscopy.

Characterization of PVA/cassava starch biocomposites fabricated with and without sonication using bacterial cellulose fiber loadings

This paper reports the characterization of polyvinyl alcohol (PVA)/cassava starch biocomposites. The cassava starch gel with or without ultrasonic probe treatment was mixed with PVA gel then short bacterial cellulose fibers were added. The presence of the sonicated starch gel in the PVA resulted in low thermal and moisture resistance, and low transparency of the blend film. After adding the fibers thermal and moisture resistance of the sonicated biocomposite increased due to stronger hydrogen bonding between the fibers and the matrix. Tensile strength of sonicated biocomposite with 10 g fibers increased 215% compared to the sonicated blend. However, addition of the fibers to the non-sonicated blend did not significantly increase mechanical and thermal properties or moisture resistance of the biocomposite. Opacity of the non-sonicated biocomposite was lower than that of the sonicated one.

Populus tremula, Nerium oleander and Pergularia tomentosa seed fibers as sources of cellulose and lignin for the bio-sorption of methylene blue

Cellulose-based substrates could represent potential funds for the sorption of pollutants. Herein, methylene blue was selected for demonstrating the bio-sorption efficiency of Nerium oleander, Pergularia tomentosa and Populus tremula seed fibers. Their cellulose contents were 45%, 43.8% and 60%. Their lignin amounts were 21%, 8.6% and 12%, respectively. Fourier Transform InfraRed suggested that the interaction of these bio-products with methylene blue could occur between hydroxyl and ester groups of cellulose and lignin and the sulfur and nitrogen atoms of the dye. Scanning Electron Microscopy showed a swelling of the bio-matters after dye biosorption. From X-Ray Diffraction, the shifting for higher values of the peaks related to the amorphous phase indicated the establishment of new rearranged regions. Such change from the decomposition behavior event studied by Thermogravimetric Analysis/Differential Thermal Analysis revealed that methylene blue was interacted with cellulose and lignin structures. The effect of adsorbent dosage, pH, time, dye concentration and temperature was investigated in controlled batch experiments. Excellent sorption capacities followed the order: Nerium oleander (280.2 mg g^-1) > Populus tremula (168 mg g^-1) > Pergularia tomentosa (145.3 mg g^-1). Freundlich fitted best the equilibrium data suggesting cooperative interactions via physisorption and chemisorption phenomenon. Kinetic data complied well with the pseudo-second-order suggesting a chemisorption mechanism.

Adsorptive Removal of Hexavalent Chromium by Diphenylcarbazide-Grafted Macadamia Nutshell Powder

Macadamia nutshell powder oxidized by hydrogen peroxide solutions (MHP) was functionalized by immobilizing 1,5′-diphenylcarbazide (DPC) on its surface. The effectiveness of grafting was confirmed by the Fourier transform infrared spectrum due to the presence of NH and C=C stretches at 3361, 1591, and 1486 cm⁻¹, respectively, on the grafted material which were absent in the nongrafted material. Thermogravimetric analysis revealed that the presence of DPC on the surface of Macadamia shells lowered the thermal stability from 300°C to about 180°C owing to the volatile nature of DPC. Surface roughness as a result of grafting was appreciated on the scanning electron microscopy images. Parameters influencing the adsorptive removal of Cr(VI) were examined and found to be optimal at pH 2, 120 min, 150 mg/L, and 2.5 g/L. Grafting MHP with DPC leads to an increase in the Langmuir monolayer capacity from 37.74 to 72.12 mg/g. Grafting MHP with DPC produced adsorbent with improved removal efficiency for Cr(VI).

Converting untreated waste office paper and chitosan into aerogel adsorbent for the removal of heavy metal ions

The utilization of waste paper, an obsolete recyclable resource, helps to save resources and protect environment. In this paper, an aerogel was prepared to convert the waste paper into a useful material, which was used to adsorb heavy metal ions and handle water pollution. Combining waste office paper and chitosan, the aerogel obtained the enhanced mechanical strength, acid resistance and high adsorption capacity (up to 156.3 mg/g for Cu²⁺). This adsorption process obeyed the pseudo-second order model and the Langmuir model. The research showed that a coordination compound was formed between amino group and Cu²⁺ during the adsorption process. The adsorbent could be regenerated well in 0.1 M H₂SO₄ with up to 98.3% desorption efficiency. The low cost, environmental friendliness, excellent adsorption capacity and regeneration ability made this novel aerogel a promising adsorbent for heavy metal ions. And this conversion is an effective reuse way of waste paper too.

Preparation of nano-sized particles from bacterial cellulose using ultrasonication and their characterization

As more applications for nano-sized natural particles are discovered, simple, environmentally friendly ways to produce these particles become more important. This work prepares and characterizes nano-size bacterial cellulose particles using ultrasonication. Pellicle from nata de coco containing nanofibers was broken up in an electrical blender, then sonicated using an ultrasonic probe at 20 kHz and 3 W/mL for 30, 60 and 90 min. Transmission electron microscope observations indicate the particles become nano-sized after 60 min ultrasound. The maximum decomposition temperature before sonication was 373 °C, decreased to 357 °C after 60 min ultrasonication. Moisture absorption of the 90 min sonicated particles film is 60% slower compared to non-sonicated particles. After ultrasonication, the crystallinity index of the cellulose decreases. The functional groups of non-sonicated and sonicated cellulose remain the same. This study promotes a potential method of fabrication of nano-sized particles from pure bacterial cellulose.