Preparation and adsorption behavior for brilliant blue X-BR of the cost-effective cationic starch intercalated clay composite matrix

Recent Developments in the Removal of Dyes from Water by Starch-Based Adsorbents

Starch-based adsorbents have demonstrated excellent potential for the removal of various noxious dyes from wastewater. This review critically evaluates the recent progress in applications of starch-based adsorbents for the removal of dyes from water. The synthesis methods of starch-based composites and their effects on physicochemical characteristics of produced adsorbents are discussed. The removal of various dyes by starch-based adsorbents are described in detail, with emphasis on the effect of key parameters, adsorption mechanism and their reusability potential. The key challenges related to the synthesis and applications of starch-based adsorbents in water purification are highlighted. Based on the research gaps, recommendations for future research are made. The evaluation of starch-based adsorbents would contribute to the development of sustainable water treatment options in near future.

Cationic starch intercalated montmorillonite nanocomposites as natural based adsorbent for dye removal

Cationic starch intercalated montmorillonite (Mt-CST) adsorbent was developed for the removal of basic dyes, namely, Basic Blue (BB66) and Basic Yellow (BY1) from aqueous solution. Cationic starches (CST) containing ammonium groups with the degree of substitution of 0.16 (CST1) and 0.69 (CST2) were successfully prepared from the reaction of low molar mass starch with (3-chloro-2-hydroxypropyl trimethyl) ammonium chloride. A series of Mt-CST nanocomposites were prepared by controlling the mass ratios of Mt:CST. Adsorption of BB66 and BY1 from aqueous solution onto Mt-CST was studied. The adsorption capacity increased with decreasing of cationic groups in the CST or increasing the mass ratios of Mt:CST. The results showed that the Mt-CST11 nanocomposite with the mass ratio of Mt:CST1 of 69: 31 exhibited relatively high adsorption capacities for basic dyes. The results of adsorption behaviors of BY1 on Mt-CST11 and Mt-CST21 indicated that the adsorption processes followed well the Langmuir isotherm.

Preparation and Characterization of Potato Starch Copolymers with a High Natural Polymer Content for the Removal of Cu(II) and Fe(III) from Solutions

Cross-linked potato starch (StMBA) and starch-g-polyacrylamide materials with a high content of natural polymer from 60 to 90 wt.% (St60–St90) were synthesized by double chemical-chemical modification (grafting and cross-linking). Eco-friendly starch absorbents were tested for removal of Cu²⁺ and Fe³⁺ from aqueous solutions. The characteristics of the obtained materials (Fourier transform infrared (FTIR), differential scanning calorimetry (DSC), thermal analysis (TGA), X-Ray Diffraction (XRD) and laser scanning microscopy (LSM)) confirmed their diversity in terms of composition and structure. The effect of N,N’-Methylenebisacrylamide (MBA) and polyacrylamide (PAM) content in the starch graft copolymers, treatment time and concentration of metal ions on adsorption efficiency were investigated. The adsorption efficiency for StMBA was 14.0 mg Cu²⁺/g and 2.9 mg Fe³⁺/g, regardless of the initial concentration of ions, whereas for starch graft copolymer St60 it was 23.0 mg Cu²⁺/g and 21.2 mg Fe³⁺/g. Absorption of Fe(III) was persisted even after 2 days. Pseudo-second order model was used to investigate the adsorption mechanisms. It was found that in addition to the chemical adsorption of ions on the surface, there is sorption inside the polymer network and chelating mechanism may dominate. Satisfactory results were attributed to the adequate grafting of PAM onto starch, the ability to form complexes with metal cations and changes in material structure.

Fixed-bed adsorption of copper from aqueous media using chitosan-coated bentonite, chitosan-coated sand, and chitosan-coated kaolinite

Fixed-bed studies were performed to evaluate the removal efficiency of copper (Cu(II)) from aqueous solution using chitosan-coated bentonite (CCB), chitosan-coated sand (CCS), and chitosan-coated kaolinite (CCK). The thermal and morphological properties of CCB, CCK, and CCS were characterized using thermogravimetric analysis, Fourier transform infrared spectroscopy, and the Brunauer-Emmett-Teller method. Dynamic experiments were carried out to investigate the effect of solution pH (3.0 to 5.0) and initial Cu(II) concentration (200 to 1000 mg/L) on the time to reach breakthrough (t_b), total volume of treated effluent (V_eff), and adsorption capacity at breakthrough (q_b). Results show that increasing the initial Cu(II) concentration inhibits the column performance where lower V_eff, t_b, and q_b were obtained. Decreasing the pH from 5.0 to 3.0 led to improved removal efficiency with higher values of V_eff, t_b, and q_b. Under pH 3.0 and 200 mg/L, the maximum removal efficiency of 68.60%, 56.10%, and 58.90% for Cu(II) was attained using CCB, CCS, and CCK, respectively. The Thomas model was determined to adequately predict the breakthrough curves based on high values of coefficient of determination (R² ≥ 0.8503). Regeneration studies were carried out using 0.1 M HCl and 0.1 M NaOH solution in the saturated column of CCB, CCK, and CCS.

A TiO2/crosslinked carboxymethyl starch composite for high-efficiency adsorption and photodegradation of cationic golden yellow X-GL dye

In this paper, a crosslinked carboxymethyl starch (CCMS) was prepared with corn starch as the raw material, epichlorohydrin as the crosslinking agent, and chloroacetic acid as the etherifying agent through a series of crosslinking, alkalization, and etherification reactions, respectively. Nano-TiO₂ was loaded onto the surface of the CCMS by the sol-gel method to obtain a TiO₂/CCMS composite. The TiO₂/CCMS composite was characterized by XPS, XRD, SEM, and BET. XPS showed that the surface chemical composition of the TiO₂/CCMS composite material contained titanium; XRD diffraction patterns indicated that the crystal form of the TiO₂/CCMS composite was a combination of the CCMS and anatase TiO₂. The surface morphology obtained by SEM showed that there were nano-TiO₂ particles on the surface of the CCMS. The specific surface area of the TiO₂/CCMS composite was larger than that of CCMS. The adsorption-photodegradation performance of the TiO₂/CCMS composite was also studied under UV irradiation, and the results showed that significant adsorption-photodegradation synergies occurred.

Spectacular Selectivity in the Capture of Methyl Orange by Composite Anion Exchangers with the Organic Part Hosted by DAISOGEL Microspheres

There is a paramount need in finding sorbents endowed with selectivity in sorption of certain dyes from their mixture with other dyes from the same family. In this context, novel composite anion exchangers (CANEXs) were fabricated here by an innovative approach using silica DAISOGEL as the host for an anion exchanger (ANEX) bearing vinylbenzyl N, N-diethyl 2-hydroxyethyl ammonium moieties. Information about the outer surface versus in-pore generation of ANEX as a function of silica morphology was acquired by scanning electron microscopy. It was demonstrated that the CANEX microspheres were able to selectively capture methyl orange (MO) in binary mixtures with either methylene blue (MB) as the cationic dye or Chicago Sky Blue 6B (CSB) as the competing azo dye. The adsorption kinetics of MO and CSB were well-fitted by a pseudo-second-order model, indicating that chemisorption controlled the sorption process. Isotherms of "H" type characterized the sorption of MO, whereas "L" type isotherms described the sorption of CSB. Langmuir and Sips isotherms were the most suitable models to describe the sorption process at equilibrium. Even if only about 10 wt % of the CANEX sorbents was involved in the sorption process, the maximum sorption capacity was 180.25 mg MO/g composite and 153.86 mg CSB/g sorbent. Moreover, the CANEX sorbents exhibited a spectacular preference for MO molecules in competition with CSB at pH 5.5. Selectivity coefficient for MO in the mixture with either MB or CSB was 370 and 38.4, respectively. Removal efficiency of MO remained up to 100% after 10 consecutive sorption/desorption cycles.

Physicochemical and morphological properties of starch from fresh waxy corn kernels

The characteristics on physicochemical and morphological properties of starches were investigated in fresh waxy corn kernels. Starches were isolated from eight waxy corn genotypes at the immature kernel stage growing in Thailand. The starch content showed variation with genotypes and ranged from 77.76 to 90.97 %. Granule size distribution showed a two population of starch granules with peak values ranged from 0.8 to 1.1 μm (small) and 9.0 to 12.2 μm (large). Genotypes were also significantly different for average chain length (CL), unit chain length distribution and pasting properties. The small granule (<5 μm) was negatively correlated with CL and degree of polymerization (DP) 25-36 of amylopectin (-0.82 and -0.67, respectively, P < 0.01). And a strong relationship between trough and final viscosity was consistent with the contribution of pasting properties.

Starch/polyaniline nanocomposite for enhanced removal of reactive dyes from synthetic effluent

Starch/polyaniline nanocomposite was synthesized by chemical oxidative polymerization of aniline and was subsequently analyzed for dye removal from aqueous solution. Batch experiment results showed that nanocomposite removed 99% of Reactive Black 5, 98% of Reactive Violet 4, and decolorized 87% of dye bath effluent. The Toth isotherm model better described single component equilibrium adsorption, whereas the modified Freundlich model showed satisfactory fit for dye bath. In kinetic modeling, single system followed pseudo-second-order and dye bath followed the modified pseudo-first-order model. Fourier transform infrared spectroscopy pattern of the nanocomposite showed the participation of aromatic, amino, hydroxyl, and carboxyl groups. The results indicate that starch/polyaniline nanocomposite can be used as an effective adsorbent for removal of dyes from textile effluents.