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Modification of lignin to produce soil conditioning materials
Thesis (MEng)--Stellenbosch University, 2022.
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| Format: | Thesis |
| Language: | en_ZA |
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Stellenbosch : Stellenbosch University
2022
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| _version_ | 1867614120099971072 |
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| access_status_str | Open Access |
| author | Ngiba, Qiniso Theo-Maxwell |
| author2 | Görgens, Johann Ferdinand |
| author_browse | Görgens, Johann Ferdinand Ngiba, Qiniso Theo-Maxwell |
| author_facet | Görgens, Johann Ferdinand Ngiba, Qiniso Theo-Maxwell |
| author_sort | Ngiba, Qiniso Theo-Maxwell |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MEng)--Stellenbosch University, 2022. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/124658 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA |
| last_indexed | 2026-06-10T12:46:59.291Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2022 |
| publishDateRange | 2022 |
| publishDateSort | 2022 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/124658 Modification of lignin to produce soil conditioning materials Ngiba, Qiniso Theo-Maxwell Görgens, Johann Ferdinand Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering. Lignin Plant species Nitrogen fertilizers Soil conditioners Thesis (MEng)--Stellenbosch University, 2022. ENGLISH ABSTRACT: The decline in soil productivity demands intensive agricultural practices to maintain crop yields. Intensive agricultural practices such as tillage, low harvest residue retention, and the over-application of mineral nitrogen fertilizers lead to an unsustainable mineralization of soil organic matter (SOM). Increasing SOM may improve soil fertility for the long-term. Lignin is a precursor of humus – the stable form of SOM – and is available in abundance as a by-product from the pulp and paper industry. However, this raw material is devoid of plant nutrients and is characterized by high carbon-to-nitrogen ratios (C/N). Ammoxidation (treatment with oxygen and ammonia) incorporates nitrogen into lignin. This yields compounds with different nitrogen functional groups (organic and inorganic) that mineralize at different rates in the soil, giving the material a slow-release nitrogen characteristic. In this study, kraft lignin (KRT), soda lignin (SOD) and sodium lignosulphonate (SLS) were characterized, ammoxidized, and assessed in a plant-growth trial. The unique properties of each raw material were investigated, and subsequently how these properties influenced nitrogen enrichment during ammoxidation. Kraft lignin contained more phenolic hydroxyl groups (6.05 mmol/g) compared to SOD (3.22 mmol/g) and SLS (0.37 mmol/g). FTIR revealed that SOD and KRT contained an appreciable quantity of methoxyl groups, compared to SLS. KRT was thus anticipated to incorporate more nitrogen compared to SOD and SLS due to its higher methoxyl and phenolic group contents. The oxidative degradation of these functional groups is essential to nitrogen incorporation. Ammoxidation was conducted in a 1 L Parr reactor at 80 oC, 10 barg air pressure using 7 wt. % ammonia for 4 hours. The N-lignins had the following composition; N-KRT (2.8 N%, 18.3 C/N), N-SOD (1.9 N%, 28 C/N), and N-SLS (0.4 N%, 70 C/N). Pre-oxidation (1.5% H2O2) improved the nitrogen incorporation, yielding products with compositions: N-O1.5-KRT (3.2 N%, 14.4 C/N), N-O1.5-SOD (1.9 N%, 28 C/N), and N-O1.5-SLS (0.5 N%, 48 C/N). However, only N-O1.5-KRT met the criteria for N-lignins (C/N < 20). A stronger pre-oxidation (5% H2O2) yielded the following products; N-O5-KRT (4.02 N%, 12.3 C/N), N-O5-SOD (3.34 N%, 15.81 C/N), and N-O5-SLS (1.61 N%, 14.64 C/N), which were suitable for use as soil organic amendments. N-O5-SLS had a salt index of 63.62%, which was notably higher than N-O5-SOD (10.32%) and N-O5-KRT (16.53%). This was attributed to its high ash content. The pH of this material (8.81 pH) was also beyond the desirable range of pH 5 - pH 7, in contrast to N-O5-KRT (5.48 pH) and N-O5-SOD (6.51 pH). The N-lignins increased the water retention capacity of sandy soil, making them attractive for use as soil amendments. Plants tests were conducted over a 4-week period using mustard seedlings (Sinapis alba). Seedlings treated with N-O5-SLS started yellowing after 3 days and withered within a week after the application of the material, attributed to its high pH (8.81 pH) and salt index (63.62%), corresponding to its high ash (61.14%) and sodium (144 900 mg/kg) contents. N-O5-KRT (3.50 t/ha) and N-O5-SOD (3.21 t/ha) yielded higher fresh mass than the control (2.04 t/ha). It was concluded that KRT and SOD possessed desirable properties for ammoxidation: high phenolic hydroxyl group content, high methoxyl group content, and ease of purification (through acid precipitation) to make low ash raw materials, compared to SLS. Further studies may assess the profitability of the industrial production of N-lignins from local industrial lignins, conduct long term studies on the application of N-lignins as soil rehabilitation materials, and assess the suitability of these lignins for use in different soil types and plant species. AFRIKAANS OPSOMMING: Die afname in grondproduktiwiteit vereis intensiewe landbougebruike om gewasopbrengste te handhaaf. Intensiewe landbougebruike soos grondbewerking, lae oesresiduretensie, en die oor-toepassing van minerale stikstofkunsmis lei tot ’n onstabiele mineralisering van grond organiese materiaal (SOM). Verhoogde SOM mag grondvrugbaarheid vir die lang-termyn verbeter. Lignien is ’n voorloper van humus – die stabiele vorm van SOM – en is beskikbaar in oorvloed as ’n byproduk van die pulp-en-papier-industrie. Hierdie roumateriaal is egter sonder plantnutriënte en is gekarakteriseer deur hoë koolstof-tot-stikstofverhoudings (C/N). Ammoksidasie (behandeling met suurstof en ammonia) inkorporeer stikstof in lignien. Hierdie lewer samestellings met verskillende stikstof funksionele groepe (organies en anorganies) wat mineraliseer by verskillende tempo’s in die grond, en gee die materiaal ’n stadig vrylaatbare stikstof karakteristiek. In hierdie studie, is kraft lignien (KRT), soda lignien (SOD) en natrium lignosulfonaat (SLS) gekarakteriseer, ammoksideer, en geassesseer in ’n plantgroeitoets. Die unieke rou-materiaal is ondersoek, en vervolgens hoe hierdie eienskappe stikstofverryking gedurende ammoksidasie beïnvloed. Kraft het meer fenoliese hidroksielgroepe bevat (6.05 mmol/g) in vergelyking met SOD (3.22 mmol/g) en SLS (0.37 mmol/g). Fourier Transform Infrarooi (FTIR) het getoon dat SOD en KRT ’n merkbare hoeveelheid metoksielgroepe bevat het, in vergelyking met SLS. Dit was dus verwag dat KRT meer stikstof sou inkorporeer in vergelyking met SOD en SLS as gevolg van sy hoër metoksiel en fenoliese groep-inhoud. Die oksidatiewe degradasie van hierdie funksionele groepe is essensieel vir stikstof inkorporasie. Ammoksidasie is uitgevoer in ’n 1 L Parr-reaktor by 80 °C, 10 bar lugdruk deur 7 wt.% ammonia vir 4 ure te gebruik. Die N-lignien het die volgende komposisie: N-KRT (2.8 N%, 18.3 C/N), N-SOD (1.9 N%, 28 C/N), en N-SLS (0.4 N%, 70 C/N). Voor-oksidasie (1.5% H2O2) het die inkorporasie van stikstof verbeter, en produkte met die volgende samestellings opgelewer: N-O1.5-KRT (3.2 N%, 14.4 C/N), N-O1.5-SOD (1.9 N%, 28 C/N), en N-O1.5-SLS (0.5 N%, 48 C/N). Net N-O1.5-KRT het egter die kriteria vir N-lignien (C/N < 20) bereik. ’n Sterker voor-oksidasie (5% H2O2) het die volgende produkte opgelewer: N-O5-KRT (4.02 N%, 12.3 C/N), N-O5-SOD (3.34 N%, 15.81 C/N), en N-O5-SLS (1.61 N%, 14.64 C/N), wat gepas was vir gebruik as grond organiese wysigings. N-O5-SLS het ’n soutindeks van 63.62% gehad, wat aansienlik hoër was as N-O5-SOD (10.32%) en N-O5-KRT (16.53%). Dit is toegeskryf aan sy hoë asinhoud. Die pH van hierdie materiaal (8.81 pH) is ook buite die gewenste bestek van pH 5 tot pH 7, in kontras met N-O5-KRT (5.48 pH) en N-O5-SOD (6.51 pH). Die N-ligniene het die waterretensiekapasiteit van sanderige grond verhoog, wat dit aanloklik maak vir gebruik as grondwysigings. Planttoetse is uitgevoer oor ’n 4-weke periode deur mostertsaailinge (Sinapis alba) te gebruik. Saailinge behandel met N-O5-SLS het geel begin word na 3 dae en het verwelk binne ’n week na die toepassing van die materiaal, toegeskryf aan sy hoë pH (8.81 pH) en soutindeks (61.14%) en natriuminhoud (144 900 mg/kg). N-O5-KRT (3.50 t/ha) en N-O5-SOD (3.21 t/ha) het hoër vars massa as die kontrole (2.04 t/ha) gelewer. Dit is vasgestel dat KRT en SOD begeerlike eienskappe vir ammoksidasie het: hoë fenoliese hidroksielgroepinhoud, en gemak van suiwering (deur suurpresipitasie) om lae asroumateriale te maak, in vergelyking met SLS. Verdere studies kan die winsgewendheid van die industriële produksie van N-lignien uit plaaslike industriële lignien assesseer, langtermynstudies op die toepassing van N-lignien as grondrehabiliteerdermateriale uitvoer, en die geskiktheid van hierdie ligniene vir die gebruik in verskillende tipes grond en plantspesies assesseer. Masters 2022-03-09T09:18:36Z 2022-04-29T09:24:54Z 2022-03-09T09:18:36Z 2022-04-29T09:24:54Z 2022-04 Thesis http://hdl.handle.net/10019.1/124658 en_ZA Stellenbosch University 134 pages application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Lignin Plant species Nitrogen fertilizers Soil conditioners Ngiba, Qiniso Theo-Maxwell Modification of lignin to produce soil conditioning materials |
| title | Modification of lignin to produce soil conditioning materials |
| title_full | Modification of lignin to produce soil conditioning materials |
| title_fullStr | Modification of lignin to produce soil conditioning materials |
| title_full_unstemmed | Modification of lignin to produce soil conditioning materials |
| title_short | Modification of lignin to produce soil conditioning materials |
| title_sort | modification of lignin to produce soil conditioning materials |
| topic | Lignin Plant species Nitrogen fertilizers Soil conditioners |
| url | http://hdl.handle.net/10019.1/124658 |
| work_keys_str_mv | AT ngibaqinisotheomaxwell modificationoflignintoproducesoilconditioningmaterials |