Celiuliozės aerogelio kompozitai: gamyba, tyrimas ir taikymas

Naftos išsiliejimai pasitaiko naftos terminaluose vykdant naftos perpylimo darbus, remontuojant arba utilizuojant laivus, avarijų metu arba gręžimo metu išgaunant naftą jūroje. Po naftos išsiliejimo pasekmės vietinėms ekosistemoms ir ekonomikai gali būti jaučiamos dešimtmečius. Siekiant neutralizuoti ir pašalinti naftos teršalus iš aplinkos taikomi mechaniniai, cheminiai ir biologiniai metodai. Vienas iš cheminių metodų pašalinti vandenyje pasklidusią naftą yra sorbcinių medžiagų – aerogelių, panaudojimas. Aerogeliai – tai mažo tankio, didelio paviršiaus ploto, poringumo ir efektyvumo, mažų eksploatacinių sąnaudų ir paprasto naudojimo sorbcinės medžiagos. Dažniausiai aerogelių gamyboje naudojamos celiuliozės pagrindo atliekos, susidarančios įvairiuose gamybos ar žemės ūkio sektoriuose bei mažos likutinės vertės produktai. Šiame darbe pristatyti iš celiuliozės atliekų, tvaraus rišiklio – bulvių krakmolo ir ekologiniame ūkyje liekančio mažos pridėtinės vertės produkto – pluoštinių kanapių šiaudų pagamintų aerogelių tyrimo ir panaudojimo naftos teršalų valymui jūroje ir uosto akvatorijoje tyrimo rezultatai. Apskaičiuotas aerogelių tankis, poringumas ir ištirtas hidrofobiškumas. Nustatyta aerogelių maksimali sorbcinė geba, adsorbuojant žaliavinę naftą, mineralinę alyvą ir jūrinį dyzeliną. Įvertintos aerogelių gniuždomosios savybės, pakartotinio panaudojimo galimybės, naudojant mechaninį spaudimą naftą adsorbavusiems aerogeliams ir apskaičiuotas Jungo modulis. Baigiamąjį darbą sudaro: 88 puslapiai, 7 lentelės, 28 paveikslų, 1 priedas. Iš viso buvo pagaminta 250 skirtingos sudėties mėginių. Mėginiams atlikti 2200 aukščio, skersmens ir masės matavimai; 200 žaliavinės naftos, jūrinio dyzelino ir tepalų maksimalios sorbcinės gebos tyrimai; 1170 tankio ir poringumo skaičiavimai; 100 maksimalios bandinio deformacijos ir aerogelių regeneracijos-sorbcijos analizių.

Every year, the need for energy grows and more and more oil and its products are transported by ships. Oil spills occur at oil terminals during oil loading/unloading operations, ship repair or disposal, incidents, or offshore oil well drilling. After an oil spill, the effects on local ecosystems and economies can be felt for decades. In order, to neutralize and remove oil pollutants from the environment mechanical, chemical and biological methods are applied. One of the methods for adsorbing spilled in water oil is the use of sorbent materials – such as aerogels. Aerogels have low density, high surface area, porosity and efficiency, low operating costs and simple application. They are producing from cellulose-based wastes generated in various manufacturing or agricultural sectors. In this scientific work, aerogels were produced from paper waste, an agriculture residue – hemp and a sustainable binder – potato starch. It was established that low-value materials of biological origin are used in the production of cellulose aerogels: rice straw waste, kapok, chitosan, pulp, sugarcane pomace, paper waste, mango wood fiber, hemp and corn straw. The production of aerogels includes 4 stages: solution preparation, freezing, lyophilization and modification. The obtained aerogels are characterized by high porosity (up to 99.89%), sorption capacity (up to 34 g/g) and low density of 15.209-80.772 kg/m3. The principles of manufacturing composite aerogels using cellulose waste include preparation of the solution, their freezing at -18oC (2 days), drying in a lyophilizer at -110oC (6 days), impregnation of samples with MTMS and drying at 70oC (12 h). There was produced 250 cellulose aerogels. It was determined that the density of control samples with cellulose and starch varied from 15.209±2.099 kg/m3 (1%) to 80.772±6.454 kg/m3 (5%) depending on the total concentration of cellulose in the samples. Meanwhile, samples with embedded hemp fiber had a density of 85 percent. higher for samples with the lowest cellulose concentration – 28.193±5.481 kg/m3 (1%) and almost 3% lower for the highest concentration samples – 78.384±12.793 kg/m3 (5%). The porosity of the control samples was 98.89±0.16 percent, and the samples with hemp fiber inclusions had a porosity of 98.13±0.54 percent. The maximum water contact angle was recorded at 131o using 5 percent. cellulose concentration (K0.25-KA0.25-P5). Meanwhile, the smallest water contact angle was 100o (1% cellulose, K0.05-KA0.05-P1). This means that the samples are hydrophobic. It was found that the control samples with the lowest cellulose concentration (1 percent, K0.1-P1 and 1 percent, K0.05-KA0.05-P1) with cellulose and starch had the highest sorption capacity: marine diesel – 49,73±1.34 g/g, crude oil – 50.04±3.49 g/g, and mineral oil – 40.59±4.49 g/g. Meanwhile, samples with similar amount of cellulose and hemp fiber adsorbed marine diesel the best – 34.48±5.62 g/g and mineral oil – 30.99±6.37 and slightly less crude oil – 26.84±1.73 g /g. The results of the maximum sorption test of samples with the highest cellulose concentrations (5%, K0.5-P5 and 5%, K0.25-KA0.25-P5) were similar. The maximum sorption capacity of control samples was 10.55±0.43 g/g for marine diesel, 10.87±1.16 g/g for crude oil and 9.89±0.53 g/g for mineral oil. Meanwhile, the maximum sorption capacity of samples with hemp fiber was 10.76±1.35 g/g, 11.11±1.37 g/g and 7.27±3.05 g/g, respectively. During tests of compressive mechanical properties, it was established that a clear linear range of stresses and strains can be seen in samples of different concentrations. In dry cellulose-based samples, where starch is used as a binder, the linear region can be seen to extend from 5 to 10 percent. deformations, and in samples where starch with hemp fiber is used as a binder, this region extends a little longer – from 5 to 20 percent. deformations. The highest numerical value of Young's modulus was determined for dry control samples – 1.937 kPa (5% K0.5-P5) and for samples with hemp fiber – 446.891 kPa (5% K0.25-KA0.25-P5). The lowest density aerogels, when starch and hemp are used as additives, had 50.5 percent. better strength – 9.3 kPa than the control samples with only starch (14 kPa), while aerogels with the highest cellulose concentrations were quite similar in their strength – 250 kPa (K0.5-P5) and 256.5 kPa (K0.25- KA0.25-P5) respectively. In deformation-relaxation tests, the recovery of wet samples with the lowest concentrations (K0.1-P1 and K0.05-KA0.05-P) was similar – 56 percent. of the initial height, and from the samples with the highest concentrations (K0.5-P5 and K0.25-KA0.25-P5), the best results were shown by the control samples with starch – they recovered 61%. height. All strain-stress graphs of wet samples showed a drop in sorption efficiency after the 1st mechanical compression cycle. Hemp fiber aerogels with a sorption capacity of up to 34 g/g can be used for cleaning oil pollution in the sea and harbor waters, but their mechanical stability is still insufficient for reuse, which requires the search for other additives that provide mechanical stability. Since wet aerogels (soaked in crude oil) aerogels were used for the mechanical compressive tests, we can claim that the test results are close to the performance of aerogels under real conditions.