Delignification and characterization of Tule (Typha Dominguensis) for its potential use in the production of green concrete.

In the search to mitigate the ecological footprint originated by the construction industry, the elaboration of green concrete is an alternative. However, it is necessary to study the material and determine if it requires a treatment prior to its incorporation into the concrete mixture. Natural fibers of Typha Dominguensis were extracted and analyzed in winter and summer seasons. A process of de-lignification with H2O2 was carried out to observe transformations in the morphological, chemical and structural properties. It was found that the physicochemical properties vary according to the extraction season even when the extraction site is the same. As an example, the percentage of ash obtained doubled in winter season. By means of an optical microscope an increase in roughness was observed without showing damage to the fibers, as for the chemical and structural properties a considerable decrease in the signals attributed to non-cellulosic material is appreciated. Additionally, the crystallinity is favoured by 13.58%, the humidity and hydrophilicity of the fiber remain similar considering the extraction season, although after de-lignification this percentage tends to decrease. Finally, the research has shown that it is necessary to previously perform a de-lignification process to favour the interaction of Tule as a material that can be incorporated into a new green concrete.


Introduction
Currently, the Southern Tamaulipas Lagoon System (STLS) is experiencing an excessive growth of a plant that is known in the area as Tule or Junco (Typha Dominguensis) as shown in Figure 1, erroneously named Typha Angustifolia by some researchers.

Species Typha Dominguensis
Tule was introduced to Mexico and nowadays controlling its proliferation in fresh water has become a severe problem.It can behave as an invasive plant (weed) because it forms extensive populations exclusive to its species, it can form up to 120 shoots per m 2 , that is to say; a mother plant of Tule can produce up to 35 daughter plants per season, managing to colonize 1 to 2 m 2 , the Tule islets are known as Totorales [1].It is known that in the conurbation area dredging is carried out for its extraction.However, there is no program to control the excessive growth of the Tule and in this way the volume of water in the lagoons is reduced.Therefore, it is important and necessary to give added value to the Tule, since, if adequate environmental measures are not taken, it could lead to the gradual drying up of the lagoons and, specifically in the case of the Tamesí River Lagoon System, it could endanger the population due to the scarcity of drinking water in the metropolitan area.
There are studies that mention the use of Tule as cattle feed, paper, clothing, household items (basketry, mats, chairs), biofuel, biopolymer and elimination of heavy metals.However, it is necessary to join efforts for its control and reduction [1,4,6].In this research, the physicochemical properties of the plant are studied in different extraction seasons, as well as the transformation of the fiber after applying an oxidizing chemical treatment to eliminate its soluble sugars and evaluate its potential use in the production of green concrete, since the incorporation of Tule fiber as a partial replacement in some element of the structural concrete mix has not been studied.However, it has already proven to be a good reinforcing agent in polymeric composites and good adhesion was obtained in the matrix of the composite, its application has been in the development of ships, automobiles and in construction, making plaster in the walls of buildings in Germany [1].It is expected that the cellulose and ash obtained from the Tule in this work can have multiple applications, not only for concrete, but also as a reference of the proposed experimental design and the use of the obtained material in the creation of new sustainable materials.

Extraction process
Tule was extracted from a lagoon located at 22°19'40 "N 97°50'23 "W, near the Luis Donaldo Colosio highway adjoining to Velamar in Madero, Tamaulipas, due to its high content of Tule and the ease of extraction.
The extraction dates were February 2 and June 12, 2023, to identify its physicochemical properties in both seasons and to see if there is a difference in the extraction season.The extraction process consists of visiting the study area and extracting the plant from the bank of the water body and then place it in black bags of 39*58" for its preparation and study.

Pretreatment to the plant
After extraction, a heat treatment is applied to dehydrate and preserve the plant.The treatment consists of drying in an oven at 100 ° c for 5 hours to reach a constant mass [6].Once the heat treatment has been applied, it is necessary to separate the plant (only the stem and leaves are of interest), according to the literature consulted.These are the plant parts with the greatest fiber amount and the best mechanical performance; the root will be discriminated because in most cases it has the presence of contaminants (it absorbs heavy metals).As a next step, the size of the fiber will be reduced by means of a Nelmor grinder mill until obtaining a fiber size with respect to the size of the interest aggregate, in this case with respect to the cement.Afterwards, a sieving will be done with a mesh No. 200 (0.075 mm) in accordance with the NMX-C-084 standard.
Due to the interest of plant incorporation into the concrete mix, a chemical treatment is required for the soluble sugars elimination [4].An acid chemical treatment was applied for the soluble sugars elimination.It is consists of an immersion of the natural fiber in H2O2 which has been reported to be a good delignification treatment and does not generate toxic by-products, it will be experimented by varying the concentration (2. 5% and 5%) of H2O2 and the temperature (environment temperature, 40 and 50 °C) and 1 hour of immersion time.The immersion time is relatively short but efficient, because when increasing the immersion times the lignin elimination does not continue, on the contrary, this tends to increase by the production of hydroperoxide radicals (HO2), superoxides (O2) and in smaller quantity the hydroxides (OH).A biomass to H2O2 ratio of 1:20 w/v was used for all experiments, due to the H2O2 has not been used in the soluble sugars elimination in Tule and the effectiveness.Therefore, it is necessary to evaluate and demonstrate which experimental design (Table 2) has the best results in the soluble sugars elimination without weakening or fiber damaging.

Moisture determination
It is necessary to determine the humidity percentage after the two extraction dates of the Tule plant, as well as of the fiber obtained before and after the H2O2 treatments, the procedure follows the ASTM D 2495 standard.

Estimation of fiber water absorption
It is necessary to determine the percentage of the Tule fiber water absorption to establish the watercement ratio in the concrete design.Because during the mixing of the elements that make up the concrete, the untreated fiber can become saturated with water in a percentage of about 100% of its dry weight, it is necessary to adjust the water absorbed by the plant that the workability is not affected.
The procedure to determine the fiber water absorption percentage consists of weighing the dry Tule fibers in an analytical balance and then letting them soak for defined times; it is recommended to submerge the fibers wrapped in a fine cloth to avoid loss of material [5].Then the Tule fibers are removed from the water and weighed.In this way the equation 1 can use to calculate the Tule fibers water absorption (w).
Where: Mt is the Tule fibers weight after immersion (t) and Md is the dry Tule fibers weight [7].
The test continues until the obtained value of water absorption is stabilized.

Determination of the percentage of ash
The Tule fiber ash percentage was determined to evaluate the feasibility of its incorporation in the concrete mix according to the TAPPI 15 os-58 standard.
The percentage of ash on a dry basis is calculated using the following equation: 2.6 Fourier-transform infrared spectroscopy (FTIR) analysis FTIR analysis of the fibers was performed with an FTIR spectrophotometer with ATR accessory.Transmittance spectra were recorded at a wavelength of 500 to 4000 cm-1 with a resolution of 10 scans.The fibers were finely chopped and preconditioned prior to analysis by allowing them to dry in an oven at 105°C for 5 hours.

X-ray diffraction analysis
Using an X-ray diffractometer (XRD), Bruker brand, Model D8 Advance, a structural analysis was performed on the Tule fibers before and after the applied treatments to determine the degree of crystallinity, with a Ka radiation of Cu (λ= 1.5405 Å) in a range of (θ-2θ) from 10 to 80°.

Optical microscope analysis
The optical microscopy technique was used to evaluate the Tule fibers before and after the chemical treatment in order to identify that they were not weakened or damaged.The morphological characterization was done by means of a BX51 Microscope with an Olympus UIS (Universal Infinity System) optical infinity correction system.

FTIR analysis
In the Figure 2 shows the FTIR spectrum of untreated Tule (reference).In the spectrum can be observed around 3350 cm-1 a broad and intense band, which corresponds with the vibration of the O-H bond of the hydrogen bond.The broad absorption band reflects the hydrophilic tendency of the Tule, related to the -OH groups present in the aromatic alcohol of the main components of the fiber [7].The band around 2920 cm-1 and 2850 cm-1 is due to the asymmetric and symmetric C-H stretching of the saturated aliphatic compounds corresponding to the aliphatic residues in cellulose and hemicellulose, as well as the methyl and methylene groups of lignin [7].The band around 1730 cm -1 is assigned to the C=O of the acetyl and uronic ester groups of hemicellulose or to the carboxylic group ester bond of ferulic and p-coumaric acids of lignin and/or hemicellulose [8,9].The sharp and prominent bands at 1635 cm -1 and 1467 cm -1 correspond to the vibration of the aromatic ring and CH2 (C-H) and CH3 (C-H) bending of the aliphatic groups, respectively.The exact frequency of this vibration depends on the C=O and N-H groups, bound to the lignin [10].The band region at 1245 cm -1 represents the C-H stretching corresponding to the stretching and deformation of hemicellulose and lignin in the ether and phenol groups present.Finally, the bands at 1170 cm -1 and 1035 cm -1 correspond to asymmetric C-O-C vibration and C-O stretching respectively, assigned to CO deformation in secondary alcohol and aliphatic ether mainly from cellulose [10].Figure 3 shows the FTIR spectrum of Tule with the application of each of the treatments with respect to the reference.A considerable decrease is observed in the broad and intense band at 3350 cm -1 after the treatments, which corresponds to the vibration of the O-H bond of the hydrogen bond, present in the cellulose polysaccharides and in the O-H radicals of phenols found in the lignin.On the other hand, this band is associated with the hydrophilic nature of the fiber, indicating not only a possible elimination of lignin, but also of hydrophilicity of the fiber, a large decrease is observed in the prominent bands in the reference Tule at 2920 cm -1 and 2850 cm -1 for each treatment applied, which corresponds to the stretching of C-H groups of the methyl and methylene groups attributed to the lignin.The decrease of the bands for each treatment was almost in its totality, in 1730 cm -1 and 1635 cm -1 a considerable decrease is appreciated.Taking into account that there are still remains of hemicellulose and lignin, which shows that there was a rupture between the ester bonds of the p-coumaric acid and the lignin product of the reaction with the hydrogen peroxide.The opposite case occurs in the bands in 1170 cm -1 and 1035 cm -1 , where they were more pronounced, indicating an enrichment of cellulose, associated to the contact time for the reactions to take place.On the other hand, a band was formed at 875 cm -1 which is not seen in the untreated Tule, associated to the frequency of the C-1 group or ring frequency, characteristic of the β-glycosidic bonds of the cellulose [8,9,11].The changes in the bands are associated with a change in the crystalline structure of cellulose.Hence an increase in intensity around 875 cm -1 (the β-glycosidic bonds between the glucose units).These change in the literature were associates that to the formation of cellulose II [9]. Figure 4 shows the comparison of the untreated Tule in different extraction season, as well as the ash obtained.As for the reference Tule (untreated), the changes in the broad band at 3350 cm -1 appear to be insignificant.However, the bands 2934 cm -1 and 2842 cm -1 corresponding to the asymmetric and symmetric C-H stretching of the saturated aliphatic compounds associating to the aliphatic remains in cellulose and hemicellulose, as well as the methyl and methylene groups of the lignin decrease greatly.Additionally, the band around 1730 cm -1 assigned to the C=O of the acetyl and uronic ester groups of hemicellulose or to the ester bond of carboxylic group of ferulic and p -coumaric acids of lignin and/or hemicellulose, are associate it to a lower percentage of lignin in the month of June.These results agrees with the research of Pandey [1], which mentions that lignin can increase or decrease depending on the season of study of the plant.In the rest of the bands no significant changes are appreciated except for the band 1024 cm -1 corresponding to the asymmetric C-O-C vibration and C-O stretching respectively, assigned to the deformation of CO in secondary alcohol and aliphatic ether mainly of cellulose.Indicating an enrichment of this non-soluble compound in the second extraction season.On the other hand, concerning the obtained ash it can be observed that the bands from 3350 cm -1 to 1632 cm -1 disappear and bands appear around 1425 cm -1 with higher intensity associated to the deformation of methyl CH3 and CH2 and the Si-H vibration of the Si-CH3 group [12,13], as well as the appearance of the band near 1024 cm -1 exactly at 1037 cm -1 associated to the silicates [13].In the second extraction these bands are more intense, it is associated to a higher content of minerals in the water bodies and therefore in the ash obtained in that extraction season, the presence of minerals in the lagoons favors the propagation of emergent macrophytes such as Tule and Water Lily, contributing to the eutrophication of the lagoons.

Ash
The Tule ash percentage was determined in the two seasons of the year.The first extraction season was days before the winter end (low temperature season), on February 02, 2023, with average temperatures in the month of 15 °C and days before the beginning of summer on June 12 (high temperature season) with average temperatures of 35°C, the 2nd extraction was carried out.The results were obtained in duplicate, quantifying 14.6 of ash in the 1st extraction and 7% in the 2nd extraction, coinciding with what Pandey and collaborators (2022) [1] report in the first and second extraction that they carried out in April and October 2022 in a lagoon in northern India, where they obtained percentages of 14.63% and 5.71% respectively.In winter seasons the ash value obtained in both cases doubles although the raw material was extracted from different water bodies.These behaviour is due to the fact that changes in temperature are related to the content of minerals that can be diffused in the water bodies, the higher the mineral content the higher the ash content that can be obtained from the Tule plant.

Moisture
The moisture Tule fiber percentage was estimated on a dry basis for both extractions in duplicate, obtaining 10.09±0.07 % and 13.99±1.66% for the 1st and 2nd extraction respectively.The moisture percentage is higher in the second extraction.These behaviour is associated to environmental factors such as climate and to increasing the rainy season, especially from June to September.Comparing with the Pandey results [1] where they obtain lower moisture percentages, it can be confirmed that even though we are talking about the same plant, climate is an important factor and in the metropolitan area, specifically Tampico, it is known as one of the wettest cities in the world.

Water absorption
It is known that natural plants of vegetable origin have the capacity to absorb the water amount proportional to their dry weight, the percentage of water absorption of the Tule fiber was estimated before applying the acid chemical treatment, obtaining 97.8±1.2% of absorption, after the chemical treatment its absorption capacity decreased 12.9 ± 3.7%, these values are within the normal ranges presented by different natural fibers [6,9,14].

X-ray diffraction analysis
X-ray diffraction (XRD) analyses provided information on the influence on the crystalline structure of the Tule fiber with respect to the hydrogen peroxide treatments applied.The crystallinity degree (Xc), Braggs angles (2θ), interplanar distances (d) and crystallite size (D) were determined.In our study it was employed the method of intensities ratio, respectively Xc = Icrystlline/(Icrystalline + Iamorphous), the values obtained can be observed in Table 3 [15].
In the obtained diffractograms it can be observed that the Tule fiber is semi-crystalline, that is to say, it presents crystalline and amorphous regions.The main peaks in the diffractogram of the reference Tule present values of 20.86° and 29.41° (Figure 7), associated to the diffraction planes (002) and (102) of cellulose I α, when applying the treatment with hydrogen peroxide a transformation in the aforementioned peaks can be observed intensifying, a phase change from cellulose I α to cellulose II associated to the diffraction plane (020) was verified in 22.03°.On the other hand, the intensity in the signal of the crystalline phase of cellulose for Tule is greater when the material has been treated, since the presence of cellulose type II confers to the fiber obtained better thermal stability and better rheological properties than cellulose type I.In the diffractogram a combination of cellulose type I α, Iβ and II can be observed [16].
As for the changes in the Bragg angle and the variation of the interplanar distances observed in Table 3, they can provide information about the changes in morphology after treatment.It is observed after the treatment with hydrogen peroxide in ID 1 and ID 4 displacements at higher angles and lower values regarding the interplanar distance, which means an increase in the resistance of the material.On the other hand, the calculated percentage of crystallinity increased for the treated samples [16].

Optical microscope analysis
Optical microscopy provided very important information about the surface morphology of the reference Tule fiber with respect to those treated with H2O2 in each experiment ID.Tecnología (CONAHCyT).

Figure 1 .
Figure 1.Presence of Tule in the STLS lagoons.

Figure 4 . 7 3. 2
Figure 4. FTIR spectra of Reference Tule and the ash obtained in the first and second extraction.