Ulla Lassi

Ionic Liquids in the Pretreatment of Lignocellulosic Biomass

The fossil fuel-based economy is facing several problems and challenges, as stated by the Intergovernmental Panel on Climate Change IPCC (IPCC, 2007). These challenges involve the increasing emissions of CO2, decreasing reserves and increasing energy prices. A potential solution to the problem could be in the form of lignocellulosic biomass as an alternative and sustainable energy source of the future. It can be used to produce chemicals and biofuels, which do not compete with food production (Huber et al., 2006; Lynd et al., 1999). Extensive research into the conversion of lignocellulosic biomass is currently being undertaken all over the world. Biomass as a carbon based material is composed of a mixture of organic molecules containing carbon and hydrogen. It usually possesses atoms of oxygen and nitrogen whilst including small quantities of other elements, such as metals. The carbon used to construct biomass is absorbed from the atmosphere as carbon dioxide (CO2) by plant life, using energy from the sun. Therefore biomass is the most abundant renewable resource available. The major constituents of lignocellulosic biomass are polymeric carbohydrates (cellulose and hemicellulose) and lignin (Zhang & Zhao, 2010). The term “lignocellulosic biomass” is often used to describe the material that composes the plant cell wall, i.e. cellulose, hemicelluloses and lignin. However, the plant cell contains different layers that differ in structure and chemical composition. As a result of the organisation and interaction between these polymeric structures, the plant cell wall is naturally recalcitrant to the biological degradation (da Costa Sousa et al., 2009). Conventional methods to convert lignocellulosic materials to sugars have been in the form of acid hydrolysis or the use of high pressures and temperatures. These methods are either energy-intensive or require the recirculation of acid. There are several solvents which dissolve cellulose, but these usually degrade the cellulose during the process (Holm et al., 2009; Mosier et al., 2005). Although different process steps are necessary in order to convert the biomass to useful products, the intermediate product is mostly glucose. As indicated above, the pretreatment of lignocellulosic biomass is a significant tool in the practical conversion processes, and it will be considered in this article.

Acid mine drainage treatment using by-products from quicklime manufacturing as neutralization chemicals.

The aim of this research was to investigate whether by-products from quicklime manufacturing could be used instead of commercial quicklime (CaO) or hydrated lime (Ca(OH)2), which are traditionally used as neutralization chemicals in acid mine drainage treatment. Four by-products were studied and the results were compared with quicklime and hydrated lime. The studied by-products were partly burnt lime stored outdoors, partly burnt lime stored in a silo, kiln dust and a mixture of partly burnt lime stored outdoors and dolomite. Present application options for these by-products are limited and they are largely considered waste. Chemical precipitation experiments were performed with the jar test. All the studied by-products removed over 99% of Al, As, Cd, Co, Cu, Fe, Mn, Ni, Zn and approximately 60% of sulphate from acid mine drainage. However, the neutralization capacity of the by-products and thus the amount of by-product needed as well as the amount of sludge produced varied. The results indicated that two out of the four studied by-products could be used as an alternative to quicklime or hydrated lime for acid mine drainage treatment.

Sulphate removal over barium-modified blast-furnace-slag geopolymer

Blast-furnace slag and metakaolin were geopolymerised, modified with barium or treated with a combination of these methods in order to obtain an efficient SO4(2-) sorbent for mine water treatment. Of prepared materials, barium-modified blast-furnace slag geopolymer (Ba-BFS-GP) exhibited the highest SO4(2-) maximum sorption capacity (up to 119mgg(-1)) and it compared also favourably to materials reported in the literature. Therefore, Ba-BFS-GP was selected for further studies and the factors affecting to the sorption efficiency were assessed. Several isotherms were applied to describe the experimental results of Ba-BFS-GP and the Sips model showed the best fit. Kinetic studies showed that the sorption process follows the pseudo-second-order kinetics. In the dynamic removal experiments with columns, total SO4(2-) removal was observed initially when treating mine effluent. The novel modification method of geopolymer material proved to be technically suitable in achieving extremely low concentrations of SO4(2-) (<2mgL(-1)) in mine effluents.

Comparison of organic peracids in wastewater treatment: Disinfection, oxidation and corrosion

The use of organic peracids in wastewater treatment is attracting increasing interest. The common beneficial features of peracids are effective anti-microbial properties, lack of harmful disinfection by-products and high oxidation power. In this study performic (PFA), peracetic (PAA) and perpropionic acids (PPA) were synthesized and compared in laboratory batch experiments for the inactivation of Escherichia coli and enterococci in tertiary wastewater, oxidation of bisphenol-A and for corrosive properties. Disinfection tests revealed PFA to be a more potent disinfectant than PAA or PPA. 1.5 mg L(-1) dose and 2 min of contact time already resulted in 3.0 log E. coli and 1.2 log enterococci reduction. Operational costs of disinfection were estimated to be 0.0114, 0.0261 and 0.0207 €/m(3) for PFA, PAA and PPA, respectively. Disinfection followed the first order kinetics (Hom model or S-model) with all studied peracids. However, in the bisphenol-A oxidation experiments involving Fenton-like conditions (pH = 3.5, Fe(2+) or Cu(2+) = 0.4 mM) peracids brought no additional improvement to traditionally used and lower cost hydrogen peroxide. Corrosion measurements showed peracids to cause only a negligible corrosion rate (<6 μm year(-1)) on stainless steel 316L while corrosion rates on the carbon steel sample were significantly higher (<500 μm year(-1)).

Solid acid-catalyzed depolymerization of barley straw driven by ball milling

This study describes a time and energy saving, solvent-free procedure for the conversion of lignocellulosic barley straw into reducing sugars by mechanocatalytical pretreatment. The catalytic conversion efficiency of several solid acids was tested which revealed oxalic acid dihydrate as a potential catalyst with high conversion rate. Samples were mechanically treated by ball milling and subsequently hydrolyzed at different temperatures. The parameters of the mechanical treatment were optimized in order to obtain sufficient amount of total reducing sugar (TRS) which was determined following the DNS assay. Additionally, capillary electrophoresis (CE) and Fourier transform infrared spectrometry (FT-IR) were carried out. Under optimal conditions TRS 42% was released using oxalic acid dihydrate as a catalyst. This study revealed that the acid strength plays an important role in the depolymerization of barley straw and in addition, showed, that the oxalic acid-catalyzed reaction generates low level of the degradation product 5-hydroxymethylfurfural (HMF).

The effect of magnesium on partial sulphate removal from mine water as gypsum

The aim of this research was to investigate the effect of magnesium on the removal efficiency of sulphate as gypsum from mine water. The precipitation conditions were simulated with MINEQL + software and the simulation results were compared with the results from laboratory jar test experiments. Both the simulation and the laboratory results showed that magnesium in the mine water was maintaining sulphate in a soluble form as magnesium sulphate (MgSO4) at pH 9.6. Thus magnesium was preventing the removal of sulphate as gypsum (CaSO4·2H2O). However, change in the lime precipitation pH from 9.6 to 12.5 resulted in magnesium hydroxide (Mg(OH)2) precipitation and improved sulphate removal. Additionally, magnesium hydroxide could act as seed crystals for gypsum precipitation or co-precipitate sulphate further enhancing the removal of sulphate from mine water.

Influence of OSC material on the behaviour of metallic Pd catalysts in C2H4 and CO oxidation as well as in NO reduction

The interaction of CO, C2H4, O2, and NO reaction gas compounds over the metallic Pd/Al2O3 and Pd/OSC/Al2O3 monoliths was investigated in order to understand the behaviour of OSC material in the oxidation and reduction reactions. FT-IR gas analyser was used for the analysis of the product gas composition. Several activity experiments carried out with dissimilar feedstreams have revealed that the CexZr1–xO2 mixed oxide is an oxygen storage compound, which promotes CO and C2H4 oxidation as well as NO reduction in particular at low temperatures.

Removal of ammonium from municipal wastewater with powdered and granulated metakaolin geopolymer

ABSTRACT Ammonium removal from municipal wastewater poses challenges with the commonly used biological processes. Especially at low wastewater temperatures, the process is frequently ineffective and difficult to control. One alternative is to use ion-exchange. In the present study, a novel ion-exchanger, metakaolin geopolymer (MK-GP), was prepared, characterised, and tested. Batch experiments with powdered MK-GP indicated that the maximum exchange capacities were 31.79, 28.77, and 17.75 mg/g in synthetic, screened, and pre-sedimented municipal wastewater, respectively, according to the Sips isotherm (R2 ≥ 0.91). Kinetics followed the pseudo-second-order rate equation in all cases (kp2 = 0.04–0.24 g mg−1 min−1, R2 ≥ 0.97) and the equilibrium was reached within 30–90 min. Granulated MK-GP proved to be suitable for a continuous column mode use. Granules were high-strength, porous at the surface and could be regenerated multiple times with NaCl/NaOH. A bench-scale pilot test further confirmed the feasibility of granulated MK-GP in practical conditions at a municipal wastewater treatment plant: consistently <4 mg/L could be reached even though wastewater had low temperature (approx. 10°C). The results indicate that powdered or granulated MK-GP might have practical potential for removal and possible recovery of from municipal wastewaters. The simple and low-energy preparation method for MK-GP further increases the significance of the results.

An original ultrasonic reaction with dual coaxial frequencies for biomass processing.

An advanced dual frequency ultrasonic coaxial reactor enabling simultaneously low and high frequencies irradiating in the same direction was developed to focus both mechanical and chemical effects on a concentrated area. The prototype was straightforward employed for the conversion of a starch-based industrial waste into sugars.

Advanced Oxidation Processes in Food Industry Wastewater Treatment – A Review

The food industry uses large amounts of water for many different purposes including cooling and cleaning, as a raw material, as sanitary water for food processing, for transportation, cooking and dissolving, as auxiliary water etc. In principle, the water used in the food industry may be used as process and cooling water or boiler feed water (EC, 2006). In 2008, for example, the total industrial water consumption in Finland was 7600 million m3 of which 34.5 million m3 was used by the food processing industry (Finnish Food and Drink Industries` Federation, 2010). As a consequence of diverse consumption, the amount and composition of food industry wastewaters varies considerably. Characteristics of the effluent consist of large amounts of suspended solids, nitrogen in several chemical forms, fats and oils, phosphorus, chlorides and organic matter (Finnish Food and Drink Industries` Federation, 2005). Generally, the BOD (biochemical oxygen demand) and COD (chemical oxygen demand) of food industry wastewater is 10 or even 100 times higher than those of domestic wastewater (EC, 2006). Unpleasant odours are also a typical problem in food industry wastewaters. These odours are usually the result of gases (hydrogen sulphide, indole) produced by the anaerobic decomposition of organic matter (Metcalf & Eddy, 2003).