Nitrate-Alkaline Pulp from Non-Wood Plants
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materials Article Nitrate-Alkaline Pulp from Non-Wood Plants KateˇrinaHájková 1,* , Jiˇrí Bouˇcek 1,2,*, Petr Procházka 3 , Petr Kalous 4 and Dominik Budský 4 1 Department of Wood Processing and Biomaterials, Faculty of Forestry and Wood Sciences, Czech University of Life Science Prague, Kamýcká 1176, 165 21 Prague, Czech Republic 2 Department of Applied Ecology, Faculty of Environmental Sciences, Czech University of Life Science Prague, Kamýcká 129, 165 21 Prague, Czech Republic 3 Department of Economics, Faculty of Economics and Administration, Czech University of Life Sciences Prague, Kamýcká 129, 165 00 Prague, Czech Republic; [email protected] 4 Secondary and Higher Vocational School of Packaging Technology in Štˇetí, Kostelní 134, 411 08 Štˇetí, Czech Republic; [email protected] (P.K.); [email protected] (D.B.) * Correspondence: hajkovakaterina@fld.czu.cz (K.H.); jboucek@fld.czu.cz (J.B.) Abstract: Because there is a lack of wood resources in many countries, this work focused on pulp and paper production from the waste and agricultural residues of non-wood plants. The work aimed to pulp the nitrate-alkaline of black mustard (Brassica Nigra L.) and camelina (Camelina Sativa L.). The black mustard and the camelina were selected due to the expanding planted areas of these crops in the Czech Republic. To characterize the chemical composition of black mustard and camelina, cellulose, lignin, ash, and extractives were determined. Raw alpha-cellulose, beta-cellulose, and gamma-cellulose were also measured. The results showed that the content of lignin in non-wood plants is lower than that in softwoods. The cooked pulp was characterized by the delignification degree–Kappa number. Additionally, handsheet papers were made for selected samples of pulp. The handsheet papers were characterized by tensile index, breaking length, and smoothness and compared with commonly available papers. Citation: Hájková, K.; Bouˇcek,J.; Procházka, P.; Kalous, P.; Budský, D. Keywords: nitrate-alkaline pulp; black mustard; camelina; tensile index; chemical analysis Nitrate-Alkaline Pulp from Non-Wood Plants. Materials 2021, 14, 3673. https://doi.org/10.3390/ ma14133673 1. Introduction Besides wood pulp, the pulp and paper industry uses fibers and agricultural waste. Academic Editor: Andrea Spagnoli The fibers of linen, hemp, and cotton have been processed since the beginnings of paper- making. These fibers are used for special types of paper. Even straw, sugarcane, cotton, and Received: 14 May 2021 other non-wood plants are used in the cellulose and paper industry. In the case of choosing Accepted: 22 June 2021 the raw material, it is important to know the chemical, morphological composition, and Published: 1 July 2021 structure of the plants [1]. Wood is the primary source for the paper industry nowadays. There is a lack of wood Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in sources which suits the growing inquiry in a lot of countries. Besides wood pulp, this published maps and institutional affil- causes the fibers and waste from the agricultural industry to be used for pulp and paper iations. making. Seventy percent of raw materials in the pulp and paper industry in China and India come from non-wood plants [2]. Hemp, sisal, and linen belong among the plants that are used in papermaking. The other raw material, which is added to banknote paper production, is cotton. The field planting areas in the Czech Republic have significantly changed during the past few years, Copyright: © 2021 by the authors. according to the planted crops. The cereals sown on the largest planting areas are, for Licensee MDPI, Basel, Switzerland. This article is an open access article example, wheat, barley, or rapeseed, but there has been significant growth of corn, poppy, distributed under the terms and mustard, and camelina planting areas recently. Figure1 shows that there is a significant conditions of the Creative Commons increase in the share of technical crops together with rapeseed (canola) over the last twenty Attribution (CC BY) license (https:// years. This is also true for the area of cropland devoted to poppy seed. A decline in creativecommons.org/licenses/by/ barley, rye, and potatoes means it grows fewer food crops in the Czech Republic over the 4.0/). observed time. Materials 2021, 14, 3673. https://doi.org/10.3390/ma14133673 https://www.mdpi.com/journal/materials Materials 2021, 14, x FOR PEER REVIEW 2 of 10 Materials 2021, 14, 3673 2 of 10 decline in barley, rye, and potatoes means it grows fewer food crops in the Czech Republic over the observed time. Figure 1. Planting areas in the Czech Republic. Cereals from grain (wheat, rye, barley, oat, and corn), legumes, root crops Figure 1. Planting areas in the Czech Republic. Cereals from grain (wheat, rye, barley, oat, and corn), legumes, root crops (potatoes, sugar beet), technical crops (rapeseed, sunflower, poppy, mustard, linen, etc.), and fodder [3]. (potatoes, sugar beet), technical crops (rapeseed, sunflower, poppy, mustard, linen, etc.), and fodder [3]. The non-wood plants have chemical and morphological characteristics different from the woodThe non-wood materials, andplants this have is the chemical reason and for other morphological cooking and characteristics bleaching conditions different from [4]. the woodThe non-wood materials, plants and this are processedis the reason by thefor chemicalother cooking method, and specifically bleaching conditions the amaranth, [4]. atriplexThe and non-wood Jerusalem plants artichoke are processed [5], and rapeseed by the strawchemical [6,7 ].method, Wheat, specifically rapeseed, amaranth, the ama- andranth, lavatera atriplex are and cooked Jerusalem in peracetic artichoke acid [5], [8], and and rapeseed rapeseed st strawraw [6,7]. produced Wheat, the rapeseed, neutral sulfiteamaranth, semi-chemical and lavatera pulp are [9 cooked,10]. in peracetic acid [8], and rapeseed straw produced the neutralAnother sulfite chemical semi-chemical method pulp for pulp [9,10]. making can be the nitrate-alkaline process, where duringAnother cooking chemical in the acid, method the cellulose–lignin for pulp making bond can isbe releasedthe nitrate-alkaline hydrolytically. process, The ligninwhere isduring nitrated cooking and partly in the oxidized acid, the into cellulose–lignin nitro-lignin, whichbond is is released soluble hydrolytically. in alkalies [11]. The lignin is nitratedThis paper and aimedpartly oxidized to cook the into nitrate-alkaline nitro-lignin, which pulp of isblack soluble mustard in alkalies (Brassica [11].Nigra L.) and camelinaThis paper (Camelina aimed Sativato cookL.) the and nitrate-alkaline to examine the pulp mechanical of black properties mustard of(Brassica paper made Nigra fromL.) and these camelina pulps. We(Camelina focused Sativa this study L.) and on examiningto examine the the chemical mechanical pulping properties of agricultural of paper cropsmade and from widening these pulps. the results We focused by the this other study potential on examining raw materials the chemical for cellulose pulping fibers. of ag- ricultural crops and widening the results by the other potential raw materials for cellulose 2.fibers. Materials and Methods On the fields in the highlands of the Ore Mountains, the black mustard (Brassica Nigra L.) is2. grown, Materials whereas, and Methods in the lowlands of the Podyjí area, the camelina (Camelina Sativa L.) is harvested.On the The fields raw in materials the highlands comprise of the stems Ore andMountains, fruits, which the black make mustard up to a quarter(Brassica of Nigra the wholeL.) is grown, quantity. whereas, The chemical in the analysislowlands was of the performed Podyjí area, according the camelina to the TAPPI (Camelina Test methodsSativa L.) beforeis harvested. the cooking The raw [12 ].materials The analysis comprise for randomly stems and taken fruits, samples which make were up determined to a quarter in aof laboratorythe whole vibratory quantity. mill, The specifically chemical analysis ash (TAPPI was T 211om-02)performed and according silica (TAPPI to the T TAPPI 245 cm-98) Test contents,methods as before well as the extractive cooking contents [12]. The by analysis Soxhlet extraction for randomly with acetone,taken samples ethanol, were and with deter- a 7:3mined mixture in a of laboratory ethanol to toluenevibratory by mill, volume specifically (TAPPI T ash 280 pm-99),(TAPPI asT well211om-02) as Klason and lignin silica (TAPPI(TAPPI T T 22 245 cm-02) cm-98) using contents, 72% sulphuric as well acid. as extr Followingactive contents the extraction, by Soxhlet the cellulose extraction content with wasacetone, determined ethanol, by and the Seifertwith a method7:3 mixture described of ethanol in reference to toluene [13], andby volume alpha-cellulose, (TAPPI T beta- 280 cellulose,pm-99), as and well gamma-cellulose as Klason lignin content (TAPPI according T 22 cm-02) to TAPPI using T72% 203 sulphuric cm-99. The acid. last Following chemical analysisthe extraction, was the the water cellulose solubility content of the was raw dete materialrmined under by the the Seifert TAPPI method Test method described T207 in om-93reference and [13], the 1% and sodium alpha-cellulose, hydroxide beta-cellulose, solubility, according and gamma-cellulose to TAPPI T 212 om-88.content according to TAPPIThe raw T 203 materials cm-99.were The disintegratedlast chemical analysis into chips was of 1the cm water length solubility before the of nitrate-the raw alkaline cooking. The nitrate-alkaline cooking occurred in lab conditions by utilizing 2l boiling flasks. Each flask comprised 50 g of dry air material, and the ratio of the chemical to raw material was 20:1. The cooking process started with 45 min of cooking under the Materials 2021, 14, 3673 3 of 10 reflux condenser in 6% nitric. The washing by water was followed by the extraction in 5% sodium hydroxide when we heated the solution and then cooked for 10 min. We did not perform the heating under the reflux condenser. The additional washing by water was followed by another pulping and the neutralization by 1% acetic acid for 5 min.