8 research outputs found
Adsorption and photocatalysis in water treatment:active, abundant and inexpensive materials and methods
Abstract
Water contamination is a global problem and the growing utilization of limited water resources creates a need for efficient purification methods. Industrial effluents are polluting the natural waters, e.g. uncontrolled mining activities in developing countries have created numerous environmental hazards and different types of pollutants. This study focuses on novel adsorbents and photocatalytic materials in order to reach the aim of more efficient and affordable water treatment.
This thesis aimed at making active, efficient, and viable adsorbents out of waste materials, as well as using photocatalysis in water treatment for organic pollutants originating from different types of industries. Local Peruvian agro-waste was used as a precursor for activated carbon that was used in adsorption studies for single (As(V) and methylene blue, MB), and multicomponent mixtures (As(V)/Pb/Cd), and real polluted river water. An industrial intermediate product, hydrous TiO2, was used for As(III)/As(V) removal. Photocatalytic materials included a commercial photoactive TiO2 (P25), and tailor-made TiO2 based nanofibers (NF) decorated with Pt/Pd.
The results show that the agro-waste based activated carbons show high potential as adsorbents (e.g. ~100% As(V) removal in 2 h). With the multicomponent solution there is evidently competition for the adsorption sites; Pb was removed most efficiently. The specific surface area and pore size distribution play an important role in MB adsorption, as with As(V) the ash content is the most influential parameter. The industrial intermediate product has a high adsorption capacity towards both As(III) and As(V) (over 96% removals in 4 h), and is promising for use in natural and wastewater treatment due to its adsorption properties, availability, low cost, and non-toxicity. Photocatalysis was found to be an efficient removal method for the pollutants tested, also in the diluted industrial wastewater matrix, e.g. diuron was removed 99% in 1 h. The NFs are promising for the efficient photocatalytic degradation of organic effluents in aqueous streams such as wastewaters originating from e.g. biofuel production or fine chemicals and pharmaceutical industry. This study provides new and valuable knowledge for the purification of waters, especially when aiming at developing inexpensive water treatment materials and methods for different applications.TiivistelmÀ
Puhtaan veden puute on maailman laajuinen ongelma, ja raskasmetallien ja orgaanisten haitta-aineiden pÀÀtymistÀ ympÀristöön ja luonnonvesiin voidaan vÀhentÀÀ hyvÀllÀ ja tehokkaalla teollisuuden jÀtevesien kÀsittelyllÀ. Uusia ja tehokkaita, ympÀristön kannalta suotuisia ja kestÀviÀ vedenpuhdistustekniikoita tarvitaan erityisesti kehitysmaissa, joissa esim. kontrolloimaton kaivostoiminta aiheuttaa ympÀristö- ja terveyshaittoja.
Työn kokeellisessa osassa valmistettiin perulaisesta maatalousjÀtteistÀ aktiivihiiltÀ kemiallisella aktivoinnilla, ja seurattiin niiden kykyÀ adsorboida haitta-aineita (As(V), Pb, Cd, metyleenisini) yksi- ja monikomponenttiliuoksista ja saastuneesta luonnonvedestÀ (Puyango-Tumbesjoki, Peru). LisÀksi tutkittiin teollisuuden vÀlituotteen (TiO2) aktiivisuutta arseenin, As(III) ja As(V), adsorptiossa. ViimeisessÀ osiossa tutkittiin valokatalyysiÀ orgaanisten haitta-aineiden poistossa vesiliuoksista sekÀ kaupallisella TiO2 P25 -katalyytillÀ ettÀ kokeellisilla Pd/Pt-dopatuilla TiO2 -nanokuiduilla.
Tulokset osoittavat, ettÀ paikallisesta raaka-aineesta valmistetut aktiivihiilet ovat hyvin potentiaalisia vedenpuhdistusmateriaaleja saavuttaen jopa 100% As(V) poistuman (2h). Adsorboitavien ionien vÀlillÀ on nÀhtÀvissÀ kilpailua monikomponettiadsorptiossa; lyijyn havaittiin poistuvan tehokkaimmin tutkituissa olosuhteissa. Adsorbentin ominaispinta-ala ja huokoskokojakauma ovat tÀrkeitÀ tekijöitÀ metyleenisinin adsorptiossa, kun taas tuhkapitoisuudella on arseenin adsorptioon suurempi vaikutus. Teollisuuden TiO2-vÀlituotteella havaittiin olevan korkea adsorptiokapasiteetti sekÀ As(III)- ettÀ As(V)-spesieksiÀ kohtaan saavuttaen yli 96% poistumat (4h). Se on lupaava materiaali edelleen kehitettÀvÀksi ja kÀytettÀvÀksi esimerkiksi luonnonvesien ja jÀtevesien puhdistuksessa johtuen sen hyvistÀ adsorptio-ominaisuuksista, saatavuudesta, edullisuudesta ja myrkyttömyydestÀ. Valokatalyysin havaittiin olevan toimiva menetelmÀ orgaanisten molekyylien hajottamiseen, myös laimeasta teollisuuden jÀtevesimatriisista, esim. diuroni poistui 99% tunnissa. Nanokuitujen tapauksessa aktiivinen metalli vaikutti merkittÀvÀmmin reaktion tehokkuuteen kuin ominaispinta-ala.
TÀmÀ työ tarjoaa uutta ja tÀrkeÀÀ tietoa vesien puhdistukseen kun tavoitteena on löytÀÀ tehokas ja edullinen menetelmÀ erityyppisiin sovelluksiin
Photocatalytic degradation of perfluorooctanoic acid (PFOA) from wastewaters by TiOâ, InâOâ and GaâOâ catalysts
Abstract
The aim of the work was to prepare nanosized InâOâ and GaâOâ photocatalysts for degradation of perfluorooctanoic acid (PFOA) in water. Their commercial references along with TiOâ were used as a comparison basis. The characterization of the materials proved that successful preparation of cubic InâOâ and monoclinic ÎČ-GaâOâ were achieved via solvothermal and hydrothermal methods, respectively. The effect of different parameters such as catalyst dosage, UV light source and utilization of inorganic oxidant in PFOA treatment were evaluated. InâOâ, photocatalyst was the most efficient in the degradation of 15 mg LâÂč PFOA under UVB irradiation and synthetic air reaching 27% of degradation, which was 20 percentage points higher than for commercial InâOâ. This is proposed to be partly due to significantly higher specific surface area of the self-made InâOâ and smaller crystallite size and partly due to more efficient absorption of UVB light compared to the other tested materials. Addition of KBrOâ did not improve the activity of self-made InâOâ
Toward new benchmark adsorbents:preparation and characterization of activated carbon from argan nut shell for bisphenol A removal
Abstract
The use of argan nut shell as a precursor for producing activated carbon was investigated in this work. Two activated carbons AC-HP and AC-Na were prepared from argan nut shell by chemical activation method using phosphoric acid (HâPOâ) and sodium hydroxide (NaOH), respectively. Textural, morphological, and surface chemistry characteristics were studied by nitrogen physisorption, TGA, SEM, TXRF, FTIR, XRD, and by determining the pHPZC of the AC-HP. The adsorption experiments revealed that AC-HP was more efficient in adsorption of BPA due to high specific surface area (1372 mÂČ/g) compared to AC-Na (798 mÂČ/g). The obtained adsorption data of BPA on AC-HP correlated well with the pseudo-second-order model and the Langmuir isotherm (Qmax = 1250 mg/g at 293 K). The thermodynamic parameters (ÎG° < 0, ÎH° < 0, and ÎS° < 0) indicate that adsorption of BPA on AC-HP was spontaneous and exothermic in nature. The regeneration of AC-HP showed excellent results after 5 cycles (95â93%). This work does not only provide a potential way to use argan nut shell but also represents a sustainable approach to synthesize AC-HP, which might be an ideal material for various applications (energy storage, catalysis, and environmental remediation)
Two unconventional precursors to produce ZnClââbased activated carbon for water treatment applications
Abstract
Two unconventional raw materials, the seeds from Spondias purpurea L. (red mombin) and Inga edulis (ice cream bean), were characterized and used as precursors to produce goodâquality zinc chlorideâactivated carbons for potential use in water treatment applications. The red mombin seed was significantly more porous than the ice cream bean seed, while the activated carbons prepared from red mombin seed and ice cream bean seeds showed both a very wellâestablished microporousâmesoporous structure. Equilibrium as well as kinetic adsorption experiments were conducted with methylene blue, methyl orange, and As(V). It was revealed that both seeds are unconventional, renewable, cheap, and suitable agroâprecursors for production of activated carbons with potential application in wastewater treatment
Photocatalysis and catalytic wet air oxidation:degradation and toxicity of bisphenol A containing wastewaters
Abstract
Bisphenol A (BPA) is a commonly used chemical in consumer products. It is an endocrine disrupter that has potentially significant negative effects on human health. The use and chemical stability of BPA have resulted in the appearance of the chemical in wastewaters. Since the current wastewater treatment technologies are not effective enough to remove BPA, new methods to degrade BPA are required. In this paper, we report the efforts made towards developing a bi-functional catalyst for consecutive catalytic wet air oxidation-photocatalytic water treatment. It was found that 2.5% Pt/Ti0.8Ce0.2O2 is a potential bi-functional catalyst for the consecutive treatment. Concentration and toxicity of BPA were successfully reduced by catalytic wet air oxidation. Although BPA was further reduced by photocatalysis, it was not reflected in further decrease of cell toxicity. Thus wet-air oxidation combined with photocatalysis is a promising approach for the reduction of BPA
New insights into the genetic etiology of Alzheimerâs disease and related dementias
Characterization of the genetic landscape of Alzheimerâs disease (AD) and related dementias (ADD) provides a unique opportunity for a better understanding of the associated pathophysiological processes. We performed a two-stage genome-wide association study totaling 111,326 clinically diagnosed/âproxyâ AD cases and 677,663 controls. We found 75 risk loci, of which 42 were new at the time of analysis. Pathway enrichment analyses confirmed the involvement of amyloid/tau pathways and highlighted microglia implication. Gene prioritization in the new loci identified 31 genes that were suggestive of new genetically associated processes, including the tumor necrosis factor alpha pathway through the linear ubiquitin chain assembly complex. We also built a new genetic risk score associated with the risk of future AD/dementia or progression from mild cognitive impairment to AD/dementia. The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE Δ4 allele
Sleep apnoea is a risk factor for severe COVID-19
Background Obstructive sleep apnoea (OSA) is associated with higher body mass index (BMI), diabetes, older age and male gender, which are all risk factors for severe COVID-19.We aimed to study if OSA is an independent risk factor for COVID-19 infection or for severe COVID-19.Methods OSA diagnosis and COVID-19 infection were extracted from the hospital discharge, causes of death and infectious diseases registries in individuals who participated in the FinnGen study (n=260 405). Severe COVID-19 was defined as COVID-19 requiring hospitalisation. Multivariate logistic regression model was used to examine association. Comorbidities for either COVID-19 or OSA were selected as covariates. We performed a meta-analysis with previous studies.Results We identified 445 individuals with COVID-19, and 38 (8.5%) of them with OSA of whom 19 out of 91 (20.9%) were hospitalised. OSA associated with COVID-19 hospitalisation independent from age, sex, BMI and comorbidities (p-unadjusted=5.13Ă10â5, OR-adjusted=2.93 (95% CI 1.02 to 8.39), p-adjusted=0.045). OSA was not associated with the risk of contracting COVID-19 (p=0.25). A meta-analysis of OSA and severe COVID-19 showed association across 15 835 COVID-19 positive controls, and n=1294 patients with OSA with severe COVID-19 (OR=2.37 (95% 1.14 to 4.95), p=0.021).Conclusion Risk for contracting COVID-19 was the same for patients with OSA and those without OSA. In contrast, among COVID-19 positive patients, OSA was associated with higher risk for hospitalisation. Our findings are in line with earlier works and suggest OSA as an independent risk factor for severe COVID-19
New insights into the genetic etiology of Alzheimerâs disease and related dementias
Characterization of the genetic landscape of Alzheimerâs disease (AD) and related dementias (ADD) provides a unique opportunity for a better understanding of the associated pathophysiological processes. We performed a two-stage genome-wide association study totaling 111,326 clinically diagnosed/âproxyâ AD cases and 677,663 controls. We found 75 risk loci, of which 42 were new at the time of analysis. Pathway enrichment analyses confirmed the involvement of amyloid/tau pathways and highlighted microglia implication. Gene prioritization in the new loci identified 31 genes that were suggestive of new genetically associated processes, including the tumor necrosis factor alpha pathway through the linear ubiquitin chain assembly complex. We also built a new genetic risk score associated with the risk of future AD/dementia or progression from mild cognitive impairment to AD/dementia. The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE Δ4 allele