Microwave synthesis and adsorption performance of a novel crosslinked starch microsphere

Preparation and characterization of the bonding performance of a starch-based water resistance adhesive by Schiff base reaction

Starch is one of the important raw materials for the preparation of biomass adhesives for its good viscosity and low-cost properties. However, the drawbacks of poor water resistance and bonding performance seriously restrict its application in the wood industry. To resolve those problems, an environment-friendly renewable, and high water resistance starch-based adhesive (OSTH) was prepared with oxidized starch and hexanediamine by Schiff base reaction. In order to optimize the adhesive preparation process, the effect of different oxidation times and oxidant addition on the mechanical performance of plywood were investigated. In addition, the curing behavior characteristics, thermomechanical properties, and thermal stability of the OSTH adhesives were analyzed by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and thermogravimetric analysis (TG). Fourier-transform infrared (FTIR) spectrometry and Liquid Chromatography-Mass Spectrometry (LC-MS) were used to explain the reaction mechanisms involved. The results show this adhesive has an excellent bonding performance at the oxidation time of 12 h with 11 % (w/w, dry starch basis) NaIO4 as an oxidant. The dry shear strength, 24-hour cold water, and 3-hour hot water (63 °C) soaking shear strength of the plywood bonded with this resin were respectively 1.87 MPa, 0.96 MPa, and 0.91 MPa, which satisfied the standard requirement of GB/T 9846-2015 (≥0.7 MPa). Thus, this study provided a potential strategy to prepare starch-based wood adhesives with good bonding performance and water resistance.

An Improved Optimization Model to Predict the MOR of Glulam Prepared by UF-Oxidized Starch Adhesive: A Hybrid Artificial Neural Network-Modified Genetic Algorithm Optimization Approach

The purpose of the present article is to study the bending strength of glulam prepared by plane tree (Platanus Orientalis-L) wood layers adhered by UF resin with different formaldehyde to urea molar ratios containing the modified starch adhesive with different NaOCl concentrations. Artificial neural network (ANN) as a modern tool was used to predict this response, too. The multilayer perceptron (MLP) models were used to predict the modulus of rapture (MOR) and the statistics, including the determination coefficient (R²), root mean square error (RMSE), and mean absolute percentage error (MAPE) were used to validate the prediction. Combining the ANN and the genetic algorithm by using the multiple objective and nonlinear constraint functions, the optimum point was determined based on the experimental and estimated data, respectively. The characterization analysis, performed by FTIR and XRD, was used to describe the effect of the inputs on the output. The results indicated that the statistics obtained show excellent MOR predictions by the feed-forward neural network using Levenberg-Marquardt algorithms. The comparison of the optimal output of the actual values obtained by the genetic algorithm resulting from the multi-objective function and the optimal output of the values estimated by the nonlinear constraint function indicates a minimum difference between both functions.

A highly efficient nanoscale tapioca starch prepared by high-speed jet for Cu2+ removal in simulated industrial effluent

BACKGROUND

Nanoscale tapioca starch (NTS) was successfully developed by high-speed jet in our previous study. In this study, the adsorption capacity of Cu²⁺ onto NTS was further discussed. The optimal adsorption conditions (pH, contact time, contact temperature, initial Cu²⁺ concentration, and adsorbent concentration), adsorption kinetics, isotherms, and thermodynamic were also evaluated.

RESULTS

The results showed that NTS exhibited excellent performance in adsorption of Cu²⁺ , with adsorption capacities of 122.31 mg g^-1 for Cu²⁺ (pH 7, 0.04 g L^-1 , 0.2 g L^-1 , 313.15 K and 10 min). The pseudo-second-order and Langmuir isotherms models could be used to explain the adsorption kinetics and adsorption equilibrium, respectively. The thermodynamic results showed that the adsorption process was spontaneous and endothermic with an increase in entropy. Cu²⁺ was adsorbed onto NTS, which was confirmed by energy dispersive spectrometry analysis.

CONCLUSION

These findings indicated that NTS might be an effective, environment-friendly and renewable bio-resource adsorbent for removing heavy metals in industrial effluent. © 2021 Society of Chemical Industry.

PLGA-based biodegradable microspheres in drug delivery: recent advances in research and application

Biodegradable microspheres have been widely used in the field of medicine due to their ability to deliver drug molecules of various properties through multiple pathways and their advantages of low dose and low side effects. Poly (lactic-co-glycolic acid) copolymer (PLGA) is one of the most widely used biodegradable material currently and has good biocompatibility. In application, PLGA with a specific monomer ratio (lactic acid and glycolic acid) can be selected according to the properties of drug molecules and the requirements of the drug release rate. PLGA-based biodegradable microspheres have been studied in the field of drug delivery, including the delivery of various anticancer drugs, protein or peptide drugs, bacterial or viral DNA, etc. This review describes the basic knowledge and current situation of PLGA biodegradable microspheres and discusses the selection of PLGA polymer materials. Then, the preparation methods of PLGA microspheres are introduced, including emulsification, microfluidic technology, electrospray, and spray drying. Finally, this review summarizes the application of PLGA microspheres in drug delivery and the treatment of pulmonary and ocular-related diseases.

Preparation and Evaluation of Rice Bran-Modified Urea Formaldehyde as Environmental Friendly Wood Adhesive

In this study, defatted rice bran (RB) is used to prepare an environmentally friendly adhesive through chemical modifications. The RB is mixed with distilled water with ratios of 1:5 and 1:4 to prepare Type A and Type B adhesives, respectively having pH of 6, 8 and 10. Type A adhesive is prepared by treating RB with 1% potassium permanganate and 4% poly(vinyl alcohol), whereas Type B is formulated by adding 17.3% formaldehyde and 5.7% urea to RB. Viscosity, gel time, solid content, shear strength, Fourier transform infrared (FTIR) spectroscopy is carried out, and glass transition temperature (T g), and activation energy (E a) are determined to evaluate the performance of the adhesives. E a data reveal that adhesives prepared at mild alkaline (pH 8) form long-chain polymers. Gel time is higher in the fabricated adhesives than that of the commercial urea formaldehyde (UF). FTIR data suggest that functional groups of the raw RB are chemically modified, which enhances the bondability of the adhesives. Shear strength data indicates that bonding strength increases with increasing pH. Similar results are also observed for physical and mechanical properties of fabricated particleboards with the adhesives. The results demonstrate that RB-based adhesives can be used as a potential alternative to currently used UF-based resin.

Simultaneous Diels-Alder click reaction and starch hydrogel microsphere production via spray drying

Herein, starch was used as a raw material to produce hydrogel microspheres via a strategy that combines spray drying and a Diels-Alder reaction. First, the starch was modified with N-maleoyl alanine and succinic acid amide. Second, starch hydrogel microspheres (SGPs) and drug-loaded hydrogel microspheres (5-Fu/SGPs) were produced by spray drying an aqueous solution of the as-prepared modified starch, forming chemical crosslinks via an in situ Diels-Alder reaction during the spray drying. The microspheres slowed the release rate of 5-Fu. In vitro cytotoxicity tests indicated that the SGPs are non-toxic for model human breast cancer cells; however, the 5-Fu/SGPs demonstrated clear cytotoxicity for human breast cancer cells. Taking into account the ease of the spray drying process and the good performance of the prepared microspheres, the strategy presented here has the potential to be applied to the green preparation of drug-loaded hydrogel microspheres.

Amphoteric starch-based bicomponent modified soil for mitigation of harmful algal blooms (HABs) with broad salinity tolerance: Flocculation, algal regrowth, and ecological safety

The treatment of harmful algal blooms (HABs) by in-situ flocculation is an emerging technology capable of efficiently removing HABs from natural waters. However, differences in salinity, pH and algal species in freshwaters and seawaters can influence the flocculation treatment. In this study, we developed a bicomponent modified soil using amphoteric starch (AS) and poly-aluminium chloride (PAC) in order to effectively flocculate microalgae under broad salinity conditions. Specifically, the impacts of water salinity (0-3.3%), pH (3-11), and algal species (Microcystis aeruginosa and marine Chlorella sp.) were investigated in order to evaluate efficiency, dosage and mechanisms of algae flocculation. The results showed that AS-PAC modified soils possessed excellent resistance to salinity change due to the anti-polyelectrolyte effect of AS, which contributed to 99.9% removal efficiency of M. aeruginosa in fresh and saline waters, and Chlorella sp. in marine water, respectively. The dosage of the flocculant modifier was only 10-20% of that of another proven modifier (i.e. Moringa oleifera), which substantially reduced the material cost. The high salinity tolerance of algal flocculation by the AS-PAC modified soil was attributed to the synergistic processes of charge neutralization and netting-bridging. Thus, this study has developed a universal flocculant and revealed fundamental mechanisms for the mitigation of HABs under broad salinity conditions.

Insights into the simultaneous removal of Cr6+ and Pb2+ by a novel sewage sludge-derived biochar immobilized nanoscale zero valent iron: Coexistence effect and mechanism

Cr⁶⁺ and Pb²⁺ are both highly toxic pollutants and commonly co-exist in some industrial effluents and contaminated waters. In this study, simultaneous removal of Cr⁶⁺ and Pb²⁺ by a novel sewage sludge-derived biochar immobilized nanoscale zero-valent iron (SSB-nZVI) was systematically investigated. It was well demonstrated that a porous structure was successfully formed on the SSB-nZVI when the starch was used as an additive. A synergistic effect on the adsorption and reduction over the SSB-nZVI was achieved, resulting in nearly 90 and 82% of Cr⁶⁺ and Pb²⁺ removal within 30 min, respectively. Cr⁶⁺ was reduced prior to Pb²⁺. A low pH could accelerate the corrosion of nZVI as well as phosphate leaching. When Malachite green was added as a coexisting organic pollutant, its effective removal was found due to the formation of a Fenton-like system. The SSB-nZVI could be run consecutively three times with a relatively satisfactory performance. Most of Cr⁶⁺ was converted into Cr₂O₃ and Cr(OH)₃ on the SSB-nZVI surface, whereas most of Pb²⁺ species existed as Pb(OH)₂ (or PbO). A possible reaction mechanism on the SSB-nZVI involved the adsorption, reduction and precipitation of both Cr⁶⁺ and Pb²⁺ over the particles. Present study sheds light on the insight of the fate and transport of Cr⁶⁺ and Pb²⁺ in aquatic environment, as well provides helpful guide for the remediation of coexistence of pollutants in real applications.

Rapid and selective recovery of acetophenone from petrochemical effluents by crosslinked starch polymer

A porous crosslinked starch polymer (CSTO) using bitolylene diisocyanate as crosslinker was prepared by a facile method and used to selectively recover acetophenone (AP) from petrochemical effluent mainly containing AP and 1-phenylethanol (PE). The theoretical calculation results indicated that AP exhibited the superior affinity toward the adsorption sites of CSTO through noncovalent interactions. The adsorption measurements showed that, due to the large surface area and high affinity of phenyl rings, CSTO displayed an extremely rapid adsorption rate, a desirable adsorption capacity and selectivity to AP. The adsorption kinetics and isotherms in single solute system agreed well with the pseudo-second-order kinetic model and Freundlich isotherm model, and the adsorption was exothermic and spontaneous. Furthermore, CSTO showed excellent reusability for selective adsorption of AP from equimolar mixture of AP/PE, prompting us to further examine its applicability. In the practical application, CSTO also revealed a fast, preferential and reusable adsorption of AP from actual petrochemical effluent.

New method for quantification of dye sorption using SBA mesoporous silica as a target sorbent

In this work, a new method for the quantification of methyl violet cationic dye sorption onto SBA-15 mesoporous silica was developed. This method related the intensity of coloration of SBA-15 samples (after reached equilibrium sorption) within dye concentration in aqueous solution using Image-Pro Plus software. The sorption process of methyl violet dye onto SBA-15 was analyzed varying different initial parameters (dye concentration, mass of sorbent, pH of dye solution, and contact sorption time). SBA-15 proved as efficient sorbent for removal of methyl violet dye in contact time of 5 min, with maximum percentage of dye removal 99% at pH 8. The results obtained from Image-Pro Plus showed to be in good agreement with the sorption parameters obtained by UV/Vis spectroscopy, which has been the most commonly used instrument for quantification of dye sorption. The image analysis method proved well prediction of dye concentrations with maximum relative error of 1.83%. The advantages of this method are low cost and reliable quantitative evaluation with minimum of time.

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.

Synthesis and characterization of a starch–AlOOH–FeS2 nanocomposite for the adsorption of congo red dye from aqueous solution

This work described the synthesis and characterization of a starch–AlOOH–FeS₂ nanocomposite for the adsorption of congo red (CR) dye from aqueous solution.