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Proteins are abundant biomolecules found in human cells, as well as pathogenic bacteria and viruses. Some of them become pollutants when released into water. Adsorption is an advantageous method for separating proteins in aqueous media since proteins are already immobilized on solid surfaces. Adsorbents with surfaces rich in tannins are efficient due to their affinity for strong interactions with the various amino acids that make up proteins. This work aimed to develop an adsorbent for protein adsorption in aqueous medium using lignocellulosic materials modified from eucalyptus bark and vegetable tannins. A more efficient resin was prepared containing 10% eucalyptus bark fibers and 90% tannin mimosa by condensation with formaldehyde, and it was characterized by UV–Vis, FTIR-ATR spectroscopy and determinations of degree of swelling, bulk and bulk density and specific mass. For UV–Vis spectroscopy the percentage of condensed and hydrolysable tannins in the extracts of fibers of the dry husks of Eucalyptus Citriodora was estimated and it was also determined your soluble solids. The study of bovine serum albumin (BSA) adsorption was carried out in batch with quantification by UV–Vis spectroscopy. The most efficient prepared resin obtained 71.6 ± 2.78% removal in a solution of 260 mg L−1 of BSA working in a better pH range of the aqueous solution of BSA in its isoelectric point, ~ 5, 32 ± 0.02, under these conditions, the synthesized resin can reach a maximum BSA adsorption capacity of ~ 26.7 ± 0.29 mg g−1 in 7 min. The new synthesized resin presents good prospects for adsorption of proteins or species that in their structure have higher percentages of amino functional groups or amino acids with aliphatic, acidic and/or basic hydrophilic characteristics. [ABSTRACT FROM AUTHOR]

Quantity of water is a major concern, but the quality is of more urgent concern due to heavy metal pollution. In this study, the focus was to develop adsorbents (tannin resin (TR) and iron-doped tannin resin (Fe-TR)) from invasive Acacia mearnsii for Pb2+ and Ni2+ in solution. The developed TR and Fe-TR were prepared directly by crosslinking and iron-grafting; respectively with thermal stable at ≤ 350 °C. Surface functionality analysis revealed the presence of chelating groups at ≈ 1688 and 3661 cm−1. The crystallite sizes of the adsorbents were smaller compared to tannin; however, the % carbon and nitrogen were significantly higher. Also, the Brunauer–Emmet–Teller study revealed that iron-grafting of tannin after crosslinking increases the surface area, pore volume and pore size. Furthermore, the surface morphology of adsorbents indicated a well-defined structure with the formation of a whitish deposit and rough lump-like after ion uptake. Both adsorbents showed a type II isotherm with adsorption capacities of 40.650 mg/g and 13.763 mg/g for Pb2+and 120.63 mg/g and 110.74 for Ni2+ ion by TR and Fe-TR; respectively. The absorbate-adsorbent interactions were observed to be endothermic with negative and positive Gibb's free energy values for the adsorption of Pb2+ and Ni2+; respectively. The adsorption kinetics of Ni2+ is governed by several models; however, Pb2+ interaction is regulated by Pseudo-second-order model. Furthermore, the data generated offered the possibility of both chemisorption and physisorption processes; highlighting the flexibility and multifunctionality of tannin traps for the erasure of ion impurities in wastewater.

By using biosourced raw materials such as condensed tannins and furfuryl alcohol a biosourced thermoset resin was developed and used and tested for a new application: as a resin matrix of solid grinding wheels for angle grinders. The manufacturing procedure developed is particularly easy. Cutting and grinding discs based on this green resin were used for bonding different sizes of abrasive particles of aluminium trioxide. These discs were characterized and showed excellent abrasiveness and cutting properties. Their mechanical resistance was found to be comparable to that of commercial grinding discs bonded with synthetic phenolic resins. They tolerated well the severe stresses induced on them at 11,000 revolutions per minute (rpm) by operation in an angle grinder when grinding or cutting steel. [ABSTRACT FROM AUTHOR]

Composites were prepared by impregnating commercial nonwoven and unidirectional flax fibers mats, with a mimosa tannin/hexamine resin without addition of NaOH as it was described in previous papers and with improved results. The influence of various parameters was observed: the curing cycle including temperature, time, pressure, the moisture content, and the number of fiber mats the composites were made of. A new two-step method was investigated: full drying of the pre-impregnated mats for storage first and then rehydratation just before pressing. The composites obtained gave good modulus of elasticity and tensile strength in traction as well as a good resistance to water swelling for composites prepared with 50% matrix resin/50% natural fibers. Best results appear to be obtained using a slow curing at low temperature (130 °C for 35 min) with moisture content of 20% on dry material. [ABSTRACT FROM PUBLISHER]

Successful experiments on high, medium and low density natural fiber reinforced composites made from tannin/hexamine resin and flax-hemp fibers have recently been carried out. This study focused on the high density composites. In this work composite panels have been made of three different tannin extracts: mimosa, sulfited mimosa and quebracho, each with their own properties. The panels were tested for modulus in elasticity (MOE) in bending, and for swelling in cold water, following the French standard NF EN 622-2. It appeared that a strong correlation exists between the density and the mechanical performances of the composites. Water, which is necessary for hardening resin, can, when in excess cause a strong drop in the mechanical performances by increasing the porosity in a composite structure. In the course of carrying out this work, some manufacturing problems were found: cracks appeared during the pressing of large panels resulting in the need for a specific pressing cycle; and deformations occurred during the cooling phase due to internal stresses. Experimental procedures were developed and tested to reduce these problems. [ABSTRACT FROM AUTHOR]

• Novel cellular/non-porous foam structures were prepared via a new molding technique. • All stuffs are renewable and abundant. • Mechanical blowing was employed instead of chemical one for environmental concern. • The physical properties of this structure are outstanding in many senses. • Excellent thermal insulation and friability resistance were obtained. Recently, tannin furanic resin-based foams exhibiting excellent properties have been developed. However, its friability and thermal insulation must be improved prior to industrialization. Therefore, the tannin preconcentrate from wood bark obtained via liquefaction was mixed with furfuryl alcohol in the presence of a catalyst, surfactant, and solvent. This process includes instant in situ formation of a resin matrix, followed by spontaneous molding and curing to yield a distinct cellular/nonporous structure. Further, the cell structure, mechanical strength, friability, thermal insulation, and fire resistance properties of this material were investigated. Results indicated that the developed material displayed a distinguished bilayer structure in the form of a cellular layer crossing the interface into another nonporous layer, as revealed via scanning electron microscopy imaging. In addition, the porosity of the cellular layer was considerably lower than that observed in case of standard tannin foam. Mechanical testing demonstrated a compression strength of 0.183 and > 50 MPa (there is no yield point for the nonporous layer), and internal bond strength of 0.014 and 0.61 MPa for the cellular and nonporous layers, respectively. Rupture was always observed to occur in the cellular layer rather than at the interface. The limiting oxygen index of the cellular layer was approximately 24.51 %, which is comparable to that of the nonporous layer (28.32 %). Based on thermogravimetric analysis (TGA), the overall foam structure can easily decompose into a final residual mass of 2.8 %. Regardless, compared with other tannin foams prepared in the traditional manner by adding a foaming agent, this material exhibited superior friability resistance and thermal insulation, as corroborated from the thermal conductivity measurement (0.0239 W/m K along with an abrasion fraction of 16.49 % after friction, indicating strong durability against abrasion. [ABSTRACT FROM AUTHOR]