Synthesis of Thiourea-Graft-Polyethyleneimine and Its Performance in Flocculation of Some Inorganic Particles

Nitrophenyl Thiourea-Modified Polyethylenimine Colorimetric Sensor for Sulfate, Fluorine, and Acetate

A thiourea-based colorimetric sensor incorporating polyethyleneimine (PEI) and chromophoric nitrophenyl groups was synthesized and utilized for detecting various anions. Structural characterization of the sensor was accomplished using FTIR and 1H-NMR spectroscopy. The sensor's interactions and colorimetric recognition capabilities with different anions, including CI-, Br-, I-, F-, NO3-, PF6-, AcO-, H2PO4-, PO43-, and SO42-, were investigated via visual observation and UV/vis spectroscopy. Upon adding SO42-, F-, and AcO- anions, the sensor exhibited distinct color changes from colorless to yellow and yellowish, while other anions did not induce significant color alterations. UV/vis spectroscopic titration experiments conducted in a DMSO/H2O solution (9:1 volume ratio) demonstrated the sensor's selectivity toward SO42-, F-, and AcO-. The data revealed that the formation of the main compounds and anion complexes was mediated by hydrogen bonding, leading to signal changes in the nitrophenyl thiourea-modified PEI spectrum.

Synthesis of amino-functionalized nanocellulose by guanidine based deep eutectic solvent and its application in fine fibers retention

A guanidine-based Deep Eutectic Solvent (DES) consisting of 1,3-diaminoguanidine monohydrochloride and glycerol was utilized to prepare C-CNC from dissolving pulp. The pulp fibers were oxidized to dialdehyde cellulose by periodate, then fibrillated through the hydrogen bonds shear of DES and aminocationized through Schiff base effect of the amino groups in the DES solvent to obtain C-CNC. The results revealed that the characterization of the DES (such as viscosity, polarity, and pH) was related to the molar ratio of glycerol/guanidine-salts. The hydrogen bond network structure of DES solvent with optimal system was simulated by DFT and its damage to fiber hydrogen bond network was predicted. The C-CNC produced under the optimal reaction conditions (molar ratio of 1:2, 90 °C for 2 h) was highly dispersible with an average length and diameter of 85 ± 35 nm and 5.0 ± 1.2 nm, a charge density of 2.916 mol/g. C-CNC exhibited excellent flocculation when added to fine fiber suspensions of chemomechanical slurries, achieving rapid flocculation and settling onto fibers in <1 min. The DES solvent maintained its reactivity after 5 cycles. This study lays the foundation for the batch preparation of nanocellulose in an environmentally friendly manner and its application as a green additive in paper industry.

Abatement of some commercial fungicide content from model dispersions by a new thiourea-graft-polyethyleneimine derivative

A new derivative of polyethyleneimine (PEI) with 9% degree of substitution of its primary and secondary amino groups with thiourea moieties (TU₉-PEI) has been synthesized and investigated as flocculant in model suspensions of commercial fungicide formulations Dithane M45, Melody Compact 49 WG, Cabrio®Top, and their mixtures. The structure of TU₉-PEI, obtained by an aqueous one-pot strategy involving formaldehyde mediated coupling of PEI and TU, was confirmed by FTIR and ¹H NMR spectroscopy as well as the streaming potential measurements. The settling time, polymer dose, and fungicide type and concentration were the parameters used for assessing the flocculation ability of the new polycation sample. The UV-Vis spectroscopy measurements revealed a good removal efficiency of TU₉-PEI for all of the fungicides investigated, between 88 and 94%. Slightly higher removal percent was found for greater fungicide concentrations. The charge neutralization was indicated by zeta potential measurements (values close to zero recorded at the optimum polymer dose) as the main mechanism which contributed to the Dithane and Cabrio®Top particle removal and a combined effect of the TU₉-PEI/fungicide particle electrostatic attractions and hydrogen bonds between both the amine and thiourea groups of the polycation chains and the hydroxyl ones on the copper oxychloride particles (negative values) in case of the Melody Compact 49 WG particle separation. Particle size and surface morphology analysis data gave supplementary evidences regarding the TU₉-PEI ability to separate the fungicides investigated from simulated wastewater.

Feather-weight cryostructured thiourea-chitosan aerogels for highly efficient removal of heavy metal ions and bacterial pathogens

Designing of economically feasible and recyclable polysaccharide-based materials with thiourea functional groups for removal of specific metal ions such as Ag(I), Au(I), Pb(II) or Hg(II) remains a major challenge for environmental applications. Here, we introduce ultra-lightweight thiourea-chitosan (CSTU) aerogels engineered by combining successive freeze-thawing cycles with covalent formaldehyde-mediated cross-linking and lyophilization. All aerogels exhibited outstanding low densities (0.0021-0.0103 g/cm³) and remarkable high specific surface areas (416.64-447.26 m²/g), outperforming the common polysaccharide-based aerogels. Benefitting from their superior structural features (honeycomb interconnected pores and high porosity), CSTU aerogels demonstrate fast sorption rates and excellent performance in sorption of heavy metal ions from highly-concentrated single or binary-component mixtures (1.11 mmol Ag (I)/g and 0.48 mmol Pb(II)/g). A remarkable recycling stability was observed after five sorption-desorption-regeneration cycles when the removal efficiency was up to 80 %. These results support the high potential of CSTU aerogels in the treatment of metal-containing wastewater. Moreover, the Ag(I)-loaded CSTU aerogels exhibited excellent antimicrobial properties against Escherichia coli and Staphylococcus aureus bacterial strains, the killing rate being around 100 %. This data points towards the potential application of developed aerogels in circular economy, by employing the spent Ag(I)-loaded aerogels in the biological decontamination of waters.

Uncovering the effect of polyethyleneimine on methane production in anaerobic digestion of sewage sludge

The potential effect of polyethyleneimine as a flocculant on anaerobic digestion of sludge was investigated. Polyethyleneimine above 12 g/kg total suspended solids inhibited the entire anaerobic digestion process including solubilization, hydrolysis, acidification, and methanogenesis. The addition of 24 g/kg total suspended solids polyethyleneimine reduced methane production from 167 ± 5 L/kg volatile suspended solids in the control reactor (without polyethyleneimine) to 141 ± 5 L/kg volatile suspended solids. Polyethyleneimine bound to extracellular polymeric substances, thus enhancing sludge agglomeration and hindering the release of organics. Meanwhile, the reduction of cytochrome C impeded electron transport, consequently curbed direct interspecies electron transfer. The adsorption of carbon dioxide by amine groups also hampered methane conversion. This study elucidated the concept that polyethyleneimine reduces mass transfer in anaerobic digestion, providing new insights into the potential behavior of flocculants in sludge treatment.

Crystalline lamellar films with honeycomb structure from comb-like polymers of poly(2-long-alkyl-2-oxazoline)s

Comb-like copolymers are usually structured by grafting polymeric side chains onto main polymer chain. There are few reports of comb-on-comb polymers in which dense secondary side chains are grafted onto primary side chain. In this work, we synthesized comb polymers with grafted-on-graft side chains (c-PEI-g-Acyl) via an effective acylation reaction of comb polymers possessing polyethyleneimine (PEI) side chain with long-alkyl acyl chlorides. For comparison, we also synthesized homopolymers l-PEI-g-Acyls via reaction of linear PEI with long-alkyl acyl chlorides. Then, we investigated their crystalline feature in the film formation by XRD, DSC and SEM, and found that the polymers tend to form hexagonal lamella structures with bilayer alkyl spacing. The comb polymers c-PEI-g-Acyls and linear polymers l-PEI-g-Acyls were used in preparation of honeycomb film by the "breath-figure" process by dropping chloroform solution of the polymers on substrate. Different to many honeycomb polymeric films which are supported by amorphous phase, interestingly, our polymers easily afford honeycomb films which are supported by crystalline lamellae frames under higher humidity condition. It was found that the comb polymers of c-PEI-g-Acyls with longer PEI primary side chain and long alkyl secondary side chain have advantages in producing honeycomb film than linear polymers of l-PEI-g-Acys.