Preparation, characterization and adsorption performance of a novel anionic starch microsphere

Preparation of core-shell structured polystyrene @ graphene oxide composite microspheres with high adsorption capacity and its removal of dye contaminants

Styrene was added dropwise to graphene dispersion solution by Pickering emulsion method to fabricate polystyrene @ graphene oxide layered composite microspheres (Pst@GO) for the removal of dye pollutants from water solution. Field emission scanning electron microscope, transmission electron microscopy, energy dispersive spectrometer, Brunauer emmett teller, zeta potential analyser and Fourier transform infrared spectrometer were adopted to analyse the changes in the microstructure and functional group of Pst@GO before and after the adsorption. The effects of initial concentration, adsorbent dose, pH, adsorption temperature and time on the adsorption behaviour of RhB and MB onto Pst@GO were studied by batch experiments. The results showed that a lot of folds on the surface of Pst@GO were beneficial to improve its adsorption capacity. The maximum adsorption capacity of RhB and MB onto Pst@GO was 49.70 and 59.07 mg g^-1 at the initial concentration of 300 mg L^-1, dose 0.1 g, pH = 7.0, adsorption temperature 55°C, adsorption time 2 h. The adsorption kinetics and thermodynamics analysis indicated that the adsorption of two dyes onto Pst@GO was endothermic reaction, while electrostatic attraction and hydrogen bonding are the main driving forces for the adsorption reaction.Polystyrene @ graphene oxide layered composite microspheres (Pst@GO) were prepared by Pickering emulsion method to remove dye pollutants in water. The preparation process of Pst@GO is as follows:Figure 1 Schematic fabrication process of Pst@GO.

Stepwise Ethanol-Water Fractionation of Enzymatic Hydrolysis Lignin to Improve Its Performance as a Cationic Dye Adsorbent

In this work, lignin fractionation is proposed as an effective approach to reduce the heterogeneity of lignin and improve the adsorption and recycle performances of lignin as a cationic dye adsorbent. By stepwise dissolution of enzymatic hydrolysis lignin in 95% and 80% ethanol solutions, three lignin subdivisions (95% ethanol-soluble subdivision, 80% ethanol-soluble subdivision, and 80% ethanol-insoluble subdivision) were obtained. The three lignin subdivisions were characterized by gel permeation chromatography (GPC), FTIR, 2D-NMR and scanning electron microscopy (SEM), and their adsorption capacities for methylene blue were compared. The results showed that the 80% ethanol-insoluble subdivision exhibited the highest adsorption capacity and its value (396.85 mg/g) was over 0.4 times higher than that of the unfractionated lignin (281.54 mg/g). The increased adsorption capacity was caused by the enhancement of both specific surface area and negative Zeta potential. The maximum monolayer adsorption capacity of 80% ethanol-insoluble subdivision by adsorption kinetics and isotherm studies was found to be 431.1 mg/g, which was much higher than most of reported lignin-based adsorbents. Moreover, the 80% ethanol-insoluble subdivision had much higher regeneration yield (over 90% after 5 recycles) compared with the other two subdivisions. Consequently, the proposed fractionation method is proved to be a novel and efficient non-chemical modification approach that significantly improves adsorption capacity and recyclability of lignin.

Application of EDTA modified Fe3O4/sawdust carbon nanocomposites to ameliorate methylene blue and brilliant green dye laden water

This work explored the potential of magnetic sawdust carbon nanocomposites for cationic dyes removal from aqueous medium. EDTA modified magnetic sawdust carbon nanocomposites (EDTA@Fe₃O₄/SC ncs) were prepared by biogenic green reduction and precipitation approach. The surface properties, structure and composition of nanocomposites were characterized by HRTEM, FESEM, XRD, EDX, BET, FTIR etc. The Fe₃O₄ nanoparticles were 10-20 nm in diameters and having 14 m²/g surface area. Removal of Methylene blue (MB) and Brilliant green (BG) dyes from aqueous medium was studied in batch mode experiments. The maximum removal was achieved at neutral pH 7.0 with in 30 min. Adsorption capacity of EDTA@Fe₃O₄/SC for MB and BG dyes was 227.3 mg/g and 285.7 mg/g, respectively. Dye adsorption behaviour is well explained by Freundlich model. The rate of cationic dye adsorption is explained by pseudo-second order model. The value of thermodynamic parameters confirmed that adsorption process was spontaneous and favourable. Desorption and reusable efficiency of nanocomposites was also evaluated.

Using Natural Biomacromolecules for Adsorptive and Enzymatic Removal of Aniline Blue from Water

The present study investigated the adsorptive and enzymatic removal of aniline blue dye (AB) from aqueous solution using waxy riceprocessing waste (RW), peanut shell (PS), microbial waste of Aspergillus niger (MW) as low cost adsorbents, and laccase (Lac) as a biocatalyst. Commercial activated carbon (AC) was also employed to compare the adsorption performance with the three adsorbents. Dye removal was examined under various parameters in batch experiments. It was found that dye removal by RW and Lac was 89–94% noticeably better than that by MW and PS (20–70%). In any cases, AC produced the highest dye removal among the tested materials. The kinetics, isotherms, and thermodynamics were then analyzed to elucidate the adsorption process by the four adsorbents. The pseudo-second order kinetic was superior to the pseudo first order kinetic model in describing adsorption for all adsorbents. The Langmuir model fitted the adsorption process very well, indicating monolayer coverage of dyes on a solid surface. A thermodynamic analysis of enthalpy (ΔH°), entropy (ΔS°), and Gibbs free energy (ΔG°) classified the adsorption as a nonspontaneous and endothermic process. The results reveal diverse natural materials (e.g., processing waste RW) as novel substitutes for traditional activated carbon, as well as laccase as a green catalyst for the treatment of dye wastewater.

Starch nanoparticles prepared in a two ionic liquid based microemulsion system and their drug loading and release properties

In this work, 1-hexadecyl-3-methylimidazolium bromide ([C₁₆mim]Br) and 1-octyl-3-methylimidazolium acetate ([C₈mim]Ac) were simultaneously used as substitutes for surfactants and the polar phase to prepare ionic liquid microemulsions.

Poly-(acryl amine-co-dimethyldiallyl ammonium chloride) graft starch flocculant for cleaning-up of wastewater

Graft starch flocculant (GSF) was synthesized by copolymerization of carboxymethylated soluble starch, acryl amine and dimethyldiallyl ammonium chloride using ceric ammonium nitrate (NH4)2Ce(NO3)6 as the polymerization initiator. The morphology was observed by scanning electron microscope, the structure was characterized by Fourier transform infrared spectroscopy and the surface area was measured by the Brunauer-Emmett-Teller method. The experimental results showed that the GSF had huge pore volume, high specific area and proper reaction groups, which could enhance its ability to adsorb heavy metal ions. The adsorption behavior was investigated through batch experiments in simulated Cu(2+)and Pb(2+) ions wastewater, and adsorption characteristics were affected by many factors, such as flocculant concentration, pH of the solution and adsorption time. Finally, the optimal adsorption parameters were gained, with GSF density of 0.024 mg·L(-1), pH of 8 and a reaction time of 30 min. Application experiments adequately demonstrated that the removal ratio of Cu(2+) and Pb(2+) ions for the local wastewater reached about 50% based on the above optimized condition.

Chemical modification of starch and its application as an adsorbent material

Starch is a biopolymer of plant origin which is cheap, abundant and has many applications in food and non-food industries.

Facile fabrication of magnetic carboxymethyl starch/poly(vinyl alcohol) composite gel for methylene blue removal

This study presents a simple method to fabricate magnetic carboxymethyl starch/poly(vinyl alcohol) (mCMS/PVA) composite gel. The obtained mCMS/PVA was characterized by Fourier transform infrared (FTIR) spectra, vibrating-sample magnetometer (VSM) and scanning electron microscopy (SEM) measurements. The application of mCMS/PVA as an adsorbent for removal of cationic methylene blue (MB) dye from water was investigated. Benefiting from the combined merits of carboxymethyl starch and magnetic gel, the mCMS/PVA simultaneously exhibited excellent adsorption property toward MB and convenient magnetic separation capability. The effects of initial dye concentration, contact time, pH and ionic strength on the adsorption performance of mCMS/PVA adsorbent were investigated systematically. The adsorption process of mCMS/PVA for MB fitted pseudo-second-order model and Freundlich isotherm. Moreover, desorption experiments revealed that the mCMS/PVA adsorbent could be well regenerated in ethanol solution without obvious compromise of removal efficiency even after eight cycles of desorption/adsorption. Considering the facile fabrication process and robust adsorption performance, the mCMS/PVA composite gel has great potential as a low cost adsorbent for environmental decontamination.

Preparation of cationic starch microspheres and study on their absorption to anionic-type substance

Cationic starch microspheres (CSMs) were prepared from lab-made neutral starch-based microspheres using a cationic adsorbent, namely 3-chloro-2-hydroxypropyltrimethyl ammonium chloride, as the cationic etherifying agent. Detection by scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR), and laser diffraction techniques revealed that CSMs had coarse surfaces with good sphericity and dispersibility. Differential thermal analysis showed the lower thermostability of the CSMs' main chains. Furthermore, scores of experiments confirmed that CSMs are capable of absorption to N-(phosphonomethyl) iminodiacetic acid (PMIDA), a type of anionic substance, which is the intermediate to the preparation of glyphosate, maximally up to 95.24 mg/g. Compared with the Freundlich isotherm model, the Langmuir isotherm model can better describe the absorption process. The kinetic study showed that the pseudo-second-order model demonstrated a better correlation of the experimental data in contrast with the pseudo-first-order model. It can be therefore concluded that the rate-limiting step was the chemical absorption rather than the mass transport.

Microwave synthesis and adsorption performance of a novel crosslinked starch microsphere

A new crosslinked starch microsphere (CSM) was synthesized in a microwave-assisted inversed emulsion system with soluble starch (ST) as a raw material, MBAA as a crosslinker, and K2S2O8-NaHSO3 as an initiator. The synthesized starch microsphere was characterized and examined by scanning electron microscope (SEM), FTIR spectroscopy and adsorption isotherms of N2 at 77K. Adsorption performance was investigated in methyl violet solution. The results showed that the maximum adsorption capacity for MV was 99.3mg/g at 298 K, and the adsorption fitted pseudo-second-order kinetic model well with correlation coefficients greater than 0.99. The isothermal data obeyed the Langmuir model better compared to Freundlich model and Tempkin model, and the adsorption was exothermic and spontaneous. pH variations (2.0-10.0) did not significantly affect the adsorption of MV onto CSM.

Removal of Methylene Blue from Aqueous Effluent Using Fixed Bed of Groundnut Shell Powder

Removal of methylene blue from aqueous solution using a low-cost adsorbent groundnut shell powder (GNSP) was studied using fixed bed. Bed service depth model and Thomas model were employed to study the adsorption kinetics and to predict break-through curves for the system. Both models fit the experimental data very well with very highR2values. Percentage color removal increased with increase in bed height. It was found that adsorption potential of GNSP was in the range of 0.238 to 0.272 kg/kg of adsorbent. These results show that the GNSP can be effectively used as low-cost alternate adsorbent for the removal of pollutants from aqueous streams.