Colorless Solution Research Articles

Phase behaviors of chitosan/lignosulfonate mixed solutions

ABSTRACT The positively chitosan, CS, and negatively lignosulfonate, LGS, were statically mixed forming a series of mixed solutions. Experimentally, the light brown LGS solution was slowly flowed into the colorless CS solution to form the as-prepared CS/LGS mixed solutions. These mixing solutions presented regular bi-phases taking the LGS phase at the top and the CS phase at the bottom where the difference is the phase thickness varied with the mixing ratio variety. To keep the static mixing condition up to the 3rd, 12th and 15th days, these CS/LGS mixed solutions presented two-phase change tendencies because the CS percent greater samples kept the bi-phases and the LGS percent greater samples presented a tri-phases with a new darker yellow phase at the bottom and a new light yellow phase at the middle. This indicated that the statical mixing time has caused the electrostatic interaction occurrence between the CS and LGS solutions when the reaction degree was influenced by the mixing ratio. The particle size for the CS/LGS mixed solutions with the mixing ratio at 70/30 and 30/70 vol% both after static mixing of 15 days was analyzed and found it was smaller at about 200–300 nm in the upper phase and greater at about 1100–1300 nm in the bottom phase corresponding to the formed micelles and the precipitated aggregates, respectively. Recorded dynamic conductivity revealed that the electrostatic interaction between the CS and LGS strongly occurred after static mixing of about 300 s and the start time was controlled by the mixing ratio, especially the LGS percent.

Photoinduced Generation of the π-Conjugated Zwitterionic State in the ESIPT Fluorophore of 2,4-Bisimidazolylphenol

We demonstrate that 2,4-bis(4,5-diphenyl-1H-imidazol-2-yl)phenol (2,4-bImP) undergoes photoinduced conversion into the so-called "π-conjugated zwitterion" after causing an excited-state intramolecular proton transfer (ESIPT) reaction. The powder sample of 2,4-bImP exhibits largely Stokes-shifted fluorescence characteristics to ESIPT fluorophores. On the other hand, its originally colorless solutions become colored when exposed to UV light for several minutes, whose color depends on the type of solvent. In particular, the CHCl3 solution rapidly turns dark green with the absorption maximum around 700 nm, and the colored solution is nearly restored to original by alternating addition of acid and base. To explain such drastic and reversible color changes, we hypothesized that the occurrence of ESIPT (i.e., deprotonation of the phenol and protonation of the imidazolyl group at its 2-position) triggered the charge-separated structure between the negatively charged phenolate and the positively charged imidazoliumyl group at its 4-position, which allowed resonance with the neutral p-quinoid structure. The formation of this π-conjugated zwitterion was strongly supported by the results of 1H and 15N NMR and Raman measurements.

Evolution of UV/VIS Photoluminescence of Aged Zn(acac)2 Solutions in Correlation with Carbon Precipitation

Photoluminescent carbon nanodots (CDs), a new class of inorganic nanocarbon materials, have become a significant segments of luminescent nanomaterials in last decade. However mechanism of light emission and detailed identification of the light emitting centers is still debated. A huge number of synthesis methods were suggested, however few of them allow to monitor formation of the CDs on the early stage and development in progress. Recently we have found that zinc acetylacetonat (Zn(acac)2) in ethanol solutions tends to be hydrolysed under room temperature laboratory conditions resulting in gradual conversion of colorless and non luminescent solution to yellowish liquid accompanied by cedimentation of nonluminescent amorphous ZnO:OH. The yellow component of the solution has been identified as dispersion of carbon precipitates. The most important is that the process of hydrolysis in very slow with changing color and PL development within several months. Such a slow process allows following the details of PL development and evolution in time correlation with carbon precipitation.Ethanol solutions of Zn(acac)2 with concentrations in range of 0.1-4.0 % were prepared and their photoluminescence was monitored for time period of several months. It has been found that early stage of carbon precipitation is resulted in development of relatively narrow PL band with maximum at about 400 nm and corresponding excitation band at 360 nm. The spectrum of the emission band is excitation independent as well as excitation band is not dependent on emission wavelength. In the course of further aging and carbon precipitation the PL band is broaden and shifted to visible range with maximum intensity in range of 420-500 nm depending on excitation wavelength. Detailed emission/excitation study revealed that the visible emission band is composed of at list two components centered at about 420-450 nm and 500 nm, with the corresponding excitation bands at 365 nm and 420 nm. Time-resolved photoluminescence spectroscopy showed that the decay of low energy emission band follows the classical mono-exponential low with the characteristic time of several nanoseconds, while the behavior of high energy component can be described by the stretched exponential low with the average decay time of several nanoseconds. PL data is summarized and discussed in the terms of subnanometer molecular-like carbon emitters and core/shell structural model of amorphous carbon nanoparticles.

FAPI-04 PET/CT Using [18F]AlF Labeling Strategy: Automatic Synthesis, Quality Control, and In Vivo Assessment in Patient.

68Ga labeled FAPI is the current standard for FAPI-PET, but its batch activity is limited. [18F]AlF-NOTA-FAPI-04 is a promising alternative combining the advantages of a chelator-based radiolabeling method with the unique properties of fluorine-18. The objective of this study was to develop a quick automatic method for synthesis of [18F]AlF-NOTA-FAPI-04 using a AllinOne synthesis system, and perform PET imaging with [18F]AlF-NOTA-FAPI-04 on patients. [18F]AlF-NOTA-FAPI-04 was produced, and its quality control was conducted by HPLC equipped with a radioactive detector. [18F]AlF-NOTA-FAPI-04 PET/CT imaging was performed in normal BALB/c mice (n = 3) and 4T1 breast cancer models (n = 3) to determine its biodistribution. Then [18F]AlF-NOTA-FAPI-04 and 18F-fluorodeoxyglucose (FDG) PET/CT imaging were performed in an invasive ductal carcinoma patient (female, 54 years old). The synthesis time of [18F]AlF-NOTA-FAPI-04 was about 25 min, and the radiochemical yield was 26.4 ± 1.5% (attenuation correction, n = 10). The radiochemical purity was above 99.0% and was above 98.0% after 6 h. The product was colorless transparent solution with pH value of 7.0–7.5, and the specific activity was 49.41 ± 3.19 GBq/μmol. PET/CT imaging in mice showed that physiological uptake of [18F]AlF-NOTA-FAPI-04 was mainly in the biliary system and bladder, and [18F]AlF-NOTA-FAPI-04 highly concentrated in tumor xenografts. PET/CT imaging in the patient showed that [18F]AlF-NOTA-FAPI-04 obtained high tumor background ratio (TBR) value of 8.44 in segment V and VI, while TBR value was 2.55 by 18F-FDG. [18F]AlF-NOTA-FAPI-04 could be synthesized with high radiochemical yield and batch production by AllinOne module and show excellent diagnosis performance in cancer patients.

Supramolecular control over pH- and temperature-responsive dialkoxynaphthalene-functionalized poly(2-(dimethylamino)ethyl methacrylate) in water

In the framework of the development of multi-responsive polymer materials, a well-defined copolymer bearing supramolecular recognition units was designed based on 2-(dimethylamino)ethyl methacrylate (DMAEMA) and a dialkoxynaphthalene-functionalized monomer (NaphtA). The supramolecular host–guest interactions of this P(DMAEMA-co-NaphtA) copolymer with the electron-deficient CBPQT4+, 4Cl- cyclophane host were studied by 1H NMR spectroscopy, UV–Visible spectroscopy and isothermal titration calorimetry (ITC), revealing, a high association constant of 6.5 × 105 M−1 in water. The addition of CBPQT4+, 4Cl- to a colorless solution of the copolymer in water resulted in a purple solution due to the formation of donor–acceptor inclusion complexes, the intensity being directly proportional to the amount of host added. Investigations on the thermoresponsive behavior of the naphthalene-functionalized copolymer highlighted that the cloud point temperature is directly proportional to the amount of CBPQT4+, 4Cl- host added and can simply be programmed within a temperature window from 30 °C to 48 °C by playing with pH. The dethreading process was studied as function of temperature and anionic exchange of the counterions of the CBPQT4+, 4Cl-. Interestingly, a partial decomplexation was observed by heating the sample above the cloud point temperature while a complete and programmable dethreading was achieved by adding the anionic surfactant sodium dodecyl sulfate (SDS) as a competitive counterion of the host molecule.

1H-indole-based chemosensors for the sequential recognition of Hg2+ and CN− ions

Abstract Сhemosensors based on 1H-indole, 1H-benzo[e]indole, and 1H-benzo[g]indole were synthesized. According to 1H, 13C NMR, X-ray diffraction study and DFT calculations, they exist predominantly in keto form, which absorbs at 371–404 nm and exhibit a low-intensity fluorescence at 454–527 nm. Recognition of Hg2+ cations in acetonitrile results in a bathochromic shift of the long-wave absorption band by ∼20 nm, accompanied by a “naked-eye” effect that causes the colorless solution to turn bright yellow. At the same time, the emission of sensors is completely quenched. The in situ mercury(II) complexes sequentially and selectively detect CN− anions with full restoration of the initial absorption and fluorescence spectra. The fluorescence “on–off–on” cycles generated by the consistent addition of Hg2+ and CN− ions provide the obtained compounds with the properties of ionochromic molecular switch. The values of the limit of detection are 1.8 and 0.83 μМ for Hg2+ and CN− ions, respectively.

FRET-based ‘ratiometric’ molecular switch for multiple ions with efficacy towards real-time sampling and logic gate applications

Fluorescent nanoaggregates comprised of rhodamine based amphiphilic probe has been designed, which can simultaneously detect Al 3+ , Cr 3+ and F¯ ions in the aqueous medium (pH 7.4). Mechanistic investigation indicates that both the carbonyl oxygen of the spirolactam ring and the nitrogen center of indole participate in the coordination of metal ions. Consequently, metal ion-binding induces the opening of the spirolactam ring and allows the Förster energy transfer from indole to xanthene moiety. As a result, the colorless probe solution turns pink in presence of metal ions, with ratiometric fluorescence change from blue to yellow. Further, the addition of fluoride leads to dissociation of preformed Al 3+ -complex, resulting in the fading of pink color and reverting the fluorescence signal to the original. This not only serves as a tool to discriminate between Al 3+ and Cr 3+ ion but also acts as a strategy for detecting fluoride in the aqueous medium. Thus, using a single FRET probe, ‘ratiometric’, naked-eye sensing of multiple ions was achieved. Also, considering the differential response of probe molecule towards Cr(III) and Cr(VI), a colorimetric assay for biogenic thiols was developed. Simultaneously, a combinatorial molecular logic gate was designed based on the multiple ion sensing ability of the probe molecule. Further, the system showed real-time detection of Al 3+ and Cr 3+ in natural water samples, estimation of Al 3+ in antacid tablets and fluoride in mouthwash, etc. Lastly, low-cost, reusable paper strips were developed, which offers an alternative strategy for on-site detection of metal ions without engaging any sophisticated instruments or trained personnel. • Ratiometric sensing of Al 3+ , Cr 3+ and F − ions at nanomolar levels in water. • Assay for biogenic thiols based on differential response for Cr(III) and Cr(VI). • Design combinatorial logic gate based on multiple ion sensing. • Analysis of real-life samples: fluoride in mouthwash, Aluminium in antacid tablets. • Low-cost, reusable paper strips for onsite detection of ions.

Silver Diamine Fluoride: Extending the spectrum of Preventive Dentistry, a literature review

Abstract Dental caries continues to be a severe oral health problem despite a decrease in its prevalence over the past few decades. The contemporary philosophy of caries management has shifted from the traditional approach to a newer medical one, that frequently includes utilization of fluoridated and antimicrobial agents. Among these different agents, Silver Diamine Fluoride (SDF)∗ has gained significant recognition. Dr Nishino and Dr Yamaga in Japan, pioneered its application to arrest caries. It is an alkaline, colourless solution composed of diamine-silver and fluoride ions having silver's antibacterial and fluoride's remineralising property. It has been used successfully to arrest and prevent caries in deciduous and permanent teeth, prevent recurrence of secondary caries and treat dentinal hypersensitivity. No adverse systemic effects due to SDF have been noted although black discolouration following its application has raised concerns. When used wisely it is an effective, sustainable and inexpensive option for children with high caries risk, for individuals who cannot endure conventional modalities of restorative treatment and those with special health-care needs. The current review is an insight into the clinical significance and application of SDF based on published literature.

Substituent-Mediated Transformation of Polynuclear Gold(I)-Sulfido Complexes—From Pentanuclear to Octadecanuclear Cluster-to-Cluster Transformation

Substituent-Mediated Transformation of Polynuclear Gold(I)-Sulfido Complexes—From Pentanuclear to Octadecanuclear Cluster-to-Cluster Transformation

Improving the decolorization of glycerol by adsorption using activated carbon derived from oil palm biomass.

This study provides insight into the decolorization strategy for crude glycerol obtained from biodiesel production using waste cooking oil as raw material. A sequential procedure that includes physico-chemical treatment and adsorption using activated carbon from oil palm biomass was investigated. The results evidenced decolorization and enrichment of glycerol go hand in hand during the treatment, achieving >89% color removal and > 98% increase in glycerol content, turning the glycerol into a clear (colorless) solution. This is attributed to the complete removal of methanol, free fatty acids, and triglycerides, as well as 85% removal of water, and 93% removal of potassium. Properties of the resultant glycerol met the quality standard of BS 2621:1979. The economic aspects of the proposed methods are examined to fully construct a predesign budgetary estimation according to chemical engineering principles. The starting capital is proportionate to the number of physical assets to acquire where both entail a considerable cost at USD 13,200. Having the benefit of sizeable scale production, it reasonably reduces the operating cost per unit product. As productivity sets at 33 m3 per annum, the annual operating costs amount to USD 79,902 in glycerol decolorization. This is translatable to USD 5.38 per liter glycerol, which is ~69% lower compared to using commercial activated carbon.

A novel reaction‐based fluorescent probe sensitive to pH changes in multiple intervals

AbstractA new coumarin derivative containing both imine bond and amide moiety was synthesised. It was used as a reaction‐based pH probe and was sensitive to pH changes in the intervals 1.50–4.10 and 10.20–12.86. In the pH range 1.50–4.10, the ultraviolet‐visible (UV‒vis) absorption band of the probe gradually shifted from 353 nm to 340 nm with decrease in the pH value. The colour changed from pale yellow fluorescence at pH 4.10 to blue fluorescence at pH 1.50. Meanwhile the fluorescence emission band at 501 nm gradually shifted to 560 nm accompanying a gradual enhancing in the emission intensity. This pH response is caused by the hydrolysis of the imine bond in the probe under acidic conditions (pH 1.50–4.10). The colourless probe solution turned yellow at pH range 10.20–12.86. Bathochromic shift of the fluorescence band from 501 nm gradually to 550 nm was observed with the increase of pH value from 10.20 to 12.86 accompanying a gradual enhancement of the fluorescence emission intensity, indicating that the new compound serves as a fluorescent pH probe at pH range 10.20–12.86 through a deprotonation process. Under strongly alkaline conditions with pH larger than 12.86, hydrolysis of the lactone structure in the probe occurred to produce non‐fluorescent species.

Oxidation of diclofenac in the presence of iron(II) octacarboxyphthalocyanine

This paper presents the results of the research on the influence of catalytic activity of iron(II) octacarboxyphthalocyanines (FePcOC) on the transformation of diclofenac (DCF) which is the most popular anti-inflammatory analgesic. Diclofenac poses a serious threat to the natural environment. The paper demonstrates that diclofenac, in the presence a monomeric form of iron octacarboxyphthalocyanine and hydroxyl radicals (HO•) (from H2O2), undergoes a transformation into diclofenac-2,5-iminoquinone (DCF-2,5-IQ), causing distinct changes in the UV–Vis absorption spectrum. In the presence of iron octacarboxyphthalocyanine and H2O2, the previously colourless diclofenac solution becomes intense orange. As a result, a new band at approx. 450 nm appears in the absorption spectrum. HPLC analysis has shown that the concentration of diclofenac decreases with time. TD-DFT calculations using the CAM-B3LYP/6-31+G (d, p) method have been conducted to confirm experimental data concerning the formation of a new band at λmax = 450 nm.

Radical Cyclic [3]Daisy Chains

Summary Mechanically interlocked molecules (MIMs) that undergo controllable internal motions of their component parts in more than one dimension are rare entities in the molecular world. Cyclic [2]daisy chains ([c2]DCs) are a class of MIMs that have been identified as prototypes for molecular muscles. It remains, however, a challenge to synthesize [cn]DCs with n > 2 selectively and efficiently. Herein, we report the design and synthesis of [c3]DCs employing radical and anionic templates. Two mechanically interlocked [c3]DCs with 18 positive charges were obtained in >90% yields. One [c3]DC displayed good air stability in its radical cationic form, while the other underwent reversible “co-conformational” switching between open macrocyclic and closed trisarm-shaped forms under electrochemical control. These findings provide not only two-dimensional MIMs with attractive electronic and switchable properties, but also a starting point for the design of extended molecular arrays, which could become the forerunners of adjustable molecular nets and breathable molecular membranes.

Identification and characterization of popular rice (Oryza sativa L.) varieties through chemical tests

Identification and characterization of crop varieties are crucial for ensuring the genetic purity of seeds. The present investigation was carried out to identify suitable chemical methods that are fast, reliable and easy for seed analysts, breeders and seed producers for identification of a variety. Twenty-five popular rice varieties in the seed supply chain of Tamil Nadu were subjected to phenol, modified phenol, NaOH, aroma, gelatinization temperature (alkali spreading value), GA3 and 2,4-D tests. The results of the experiment revealed that phenol and modified phenol tests changed the colour of TKM 9 and TRY 1 variety to brown but no colour change was observed in the variety I.W. Ponni variety. The NaOH test is useful for the identification of TKM 9 variety as it changed the colourless solution to red. GA3 and 2,4-D tests characterized the varieties based on the shoot growth into two and three groups respectively. However, all the variety lacked aroma and exhibited a high gelatinization temperature.

Tailored functional polymeric vesicles as smart nanostructured materials for aqueous monitoring of transition metal cations

In this study, we report the newly engineered functional polymeric vesicles as the robust nanostructured materials for the recognition and quantification of transition metal cations i.e. Hg(II) and Cr(III) as the naked eye recognition architectures in aqueous solution. The as prepared visual detector was synthesized by the combination of a hyperbranched poly(3-ethyl-3-oxetanemethanol)-star-poly(ethylene oxide) (HBPO-star-PEO, HSP) functionalized with rhodamine-2-amino-5-bromopyrimidine based chemosensor (RBP). The nanostructured vesicular sensor was regarded as HSP-RBP sensor. The naked eye detection owes from the spriolactam ring opening of the rhodamine based sensor (RBP) which was grafted onto the multiarm hyperbranched amphiphilic polymer. This newly synthesized sensor can facilely self-assemble into vesicles with enriched RBP groups on the outer surface of amphiphilic polymer. As a result of the introduction of these analytes (Hg2+/Cr3+) the structural changes of RBP takes place and a transition in color change from colorless solution to pink colored solution takes place. This transition of color can clearly be seen with bare eye. Therefore, the term visual detection can be coined for the vesicular sensor. Furthermore, the limit of detection for Hg2+ and Cr3+ was calculated as low as 1.2 and 2.9 μM respectively. The striking feature of the newly prepared sensor, is its extraordinary ability for the recognition and quantification of Hg2+/Cr3+ with outstanding selectivity in raw water samples.

A rapid colorimetric method for determining glutathione based on the reaction between cobalt oxyhydroxide nanosheets and 3,3′,5,5′-Tetramethylbenzidine

As an antioxidant, glutathione (GSH) can react with reactive oxygen species (ROS) and heavy metals to help alleviate oxidative stress (OS) and damage in cells. Accurately measuring the GSH level is important to gauge the integrity of cell redox buffering capacity. In this work, a convenient method for qualitative and quantitative determination of GSH was developed based on the reaction between CoOOH nanosheets and 3,3′,5,5′-tetramethylbenzidine (TMB). Colorless TMB solution can be oxidized by CoOOH to oxidized TMB (oxTMB) which is blue in color. However, in the presence of GSH, CoOOH preferentially reacted with GSH, producing less oxTMB and lighting the blue color. The changes of the blue color of oxTMB can be directly observed by naked eyes and accurately measured by UV–vis absorbance at 652 nm. Based on that, GSH can be detected in a wide range from 0.1 to 300 µM with a low limit of detection of 0.08 μM which was performed with a quantitativehigh-throughput96-wellplate. In addition, GSH in human SH-SY5Y neuroblastoma cells was successfully determined using our method, and the results show excellent agreement with those measured by a commercial GSH detection kit based on the use of Ellman’s reagent.

Cyanide selective chemodosimeter in aqueous medium, on test strips and its application in real sample analysis

In this paper, synthesis, characterization and detection of CN− by the compound (N′1E,N′2E)-N′1,N′2-bis((2-hydroxynaphthalen-1-yl)methylene)oxalohydrazide (1) have been reported. Compound 1 is synthesized by the reaction of oxalyldihydrazide and 2-hydroxy-1-naphthaldehyde and characterized by FTIR, 1H NMR and ESI-Mass spectroscopy. UV–Visible spectral band of 1 is observed to be broadened and shifted to longer wavelength upon addition of CN− ion selectively in H2O-DMSO (8:2 v/v) medium. Based on the UV–Visible spectral data, the detection limit of cyanide ion for 1 is found to be 30.2 μM. Colourless solution of 1 changes to yellow in the presence of cyanide ion selectively. The same colour change is also observed on Whatman filter paper test strip. Fluorescence intensity of 1 is quenched due to the nucleophilic addition reaction of cyanide with one of the two imine carbons. 1H NMR titration of 1 with CN− ion corroborates the reaction of the latter with one of the two imine carbons of the former, leading to the appearance of cyanomethyl proton signal at 6.15 ppm and consequently, its behaviour as chemodosimeter. The above mentioned chemodosimeter nature of 1 is also validated by ESI-Mass spectroscopy data. Compound 1 is capable for the detection of CN− in water for real samples with concomitant colour change. Compound 1 behaves as selective cyanide chemodosimeter with associated change in its colour (in solution and on Whatman filter paper test strip) and fluorescence. 1H NMR titration and ESI-Mass data confirm the nucleophilic addition reaction of cyanide with 1. Compound 1 can be used for the detection of CN− in water for real samples.

Biogenic Synthesis of Gold Nanoparticles from Aspartic Acid - A Preliminary Study

A nanoparticle is an ultra-fine particle with at least one dimension between 1-100 nanometers (nm). Metallic nanoparticles are considered as most promising as they contain remarkable antibacterial properties. Gold nanoparticles are of high importance in research. Aspartic acid is an alpha amino acid and contains one amino group and one carboxylic group. The aim of the current study was to bio synthesize gold nanoparticles using aspartic acid. Gold Chloride (AuCl3) and Aspartic acid (C₄H₇NO₄) were used for the study. AuCL3 solution (0.266 M) was slowly added to 250 aspartic acid with stirring at 45°C. The mixture of the solutions was kept in a long-necked borosilicate flask and continuously stirred on a magnetic stirrer. The formation of gold nanoparticles was confirmed by the change of the colorless solution to a reddish hue. Characterization of the newly formed nanoparticles was then done. After approximately 9 hour incubation and intermittent stirring with a magnetic stirrer the solution color changed from colorless to a reddish hue, which indicated the formation of AuNPs. The spectrometric reading was recorded at a scanning range of 400–700 nm. AuNPs nanoparticles at 24 hours showed an increased intensity and a Surface Plasmon Resonance (SPR) band at 575 nm. The gold nanoparticles by Transmission electron microscopy were confirmed to be spherical in shape and of 20 nm. A simple and efficient method for the synthesis of AuNPs from the aspartic acid was demonstrated. Nano particles were formed in approx. 9 hours with peak absorbance at 24 hours at 575nm. The synthesized nanoparticles were spherical in shape, with an average size of 20 nm. The synthesized nanoparticles showed excellent plasmon resonance and optical properties.

Highly Selective and Sensitive (PPB Level) Quinolin‐Based Colorimetric Chemosensor for Cu(II)

Abstract4‐(quinolin‐2‐ylmethylene)aminophenol (QMAP) is synthesised in a one‐step synthetic process and was checked for its sensing ability towards metal ions. The molecule is found to be effective for the instantaneous selective and sensitive Cu(II) ion detection in PPB level in methanolic solution with a distinct development of orangish yellow colour from a colourless solution, which can be detected visually. The sensing ability of the QMAP towards Cu(II) is found independent on the type of counter anions and also in the presence of other metal ions. QMAP does not show any colour change in the presence of other metal salts. A 2 : 1 binding stoichiometry between QMAP and Cu(II) with a large binding constant of 3.2 x 1010 M−2 has been measured. Quantum chemical calculations have been used to understand the nature of the complex and the mechanism of the sensing.

Efficient and sustainable treatment of anionic dye wastewaters using porous cationic diatomite

How to develop an effective and cheap adsorbent for removing dyes completely from wastewaters and avoid disable adsorbent secondary pollution have great challenges for green dye and dyeing industrial production. In order to realize this aim, in this work, the porous cationic diatomite was prepared for the first time by covalently immobilizing poly-epichlorohydrin-dimethylamine onto natural diatomite, and its adsorption characteristics and sustainable utilization were investigated. The results indicated that the immobilizing reaction was found to happen both on the surface of diatomite and the inner wall of its pores. Cationic diatomite possessed a high removal efficiency to anionic dyes. The batch dye adsorption processes were endothermic and spontaneous, and better consistent with pseudo-second-order kinetic model and Freundlich isotherm model. The completely colorless effluent solution could be obtained when cationic diatomite was used as fixed-bed adsorbent, and its maximum dye adsorption capacities were more than 200 and 3 times larger than that of natural diatomite and commercial activated carbon, respectively. Most importantly, the disabled cationic diatomite could be used in colored coatings as pigment and filler simultaneously, thereby avoiding secondary pollution. In conclusion, this study can provide a green viable solution for controlling pollution in dye and dyeing industrial production.