Sugar, acid and furfural quantification in a sulphite pulp mill: Feedstock, product and hydrolysate analysis by HPLC/RID.

Waste from pulp and paper mills consist of sugar-rich fractions comprising hemicellulose derivatives and cellulose by-products. A complete characterisation of the waste streams is necessary to study the possibilities of an existing mill. In this work, four chromatographic methods have been developed to obtain the most suitable chromatographic method conditions for measuring woody feedstocks, lignocellulosic hydrolysates and cellulose pulp in sulphite pulping processes. The analysis of major and minor monosaccharides, aliphatic carboxylic acids and furfurals has been optimised. An important drawback of the spent liquors generated after sulphite pulping is their acidic nature, high viscosity and adhesive properties that interfere in the column lifetime. This work recommends both a CHO-782Pb column for the sugar analysis and an SH-1011 resin-based cross-linked gel column to separate low-molecular-weight chain acids, alcohols and furfurals. Such columns resulted in a good separation with long lifetime, wide pH operating range and low fouling issues.

Physico-Chemical Alternatives in Lignocellulosic Materials in Relation to the Kind of Component for Fermenting Purposes.

The complete bioconversion of the carbohydrate fraction is of great importance for a lignocellulosic-based biorefinery. However, due to the structure of the lignocellulosic materials, and depending basically on the main parameters within the pretreatment steps, numerous byproducts are generated and they act as inhibitors in the fermentation operations. In this sense, the impact of inhibitory compounds derived from lignocellulosic materials is one of the major challenges for a sustainable biomass-to-biofuel and -bioproduct industry. In order to minimise the negative effects of these compounds, numerous methodologies have been tested including physical, chemical, and biological processes. The main physical and chemical treatments have been studied in this work in relation to the lignocellulosic material and the inhibitor in order to point out the best mechanisms for fermenting purposes. In addition, special attention has been made in the case of lignocellulosic hydrolysates obtained by chemical processes with SO2, due to the complex matrix of these materials and the increase in these methodologies in future biorefinery markets. Recommendations of different detoxification methods have been given.

Metal release from contaminated estuarine sediment under pH changes in the marine environment.

The contaminant release from estuarine sediment due to pH changes was investigated using a modified CEN/TS 14429 pH-dependence leaching test. The test is performed in the range of pH values of 0-14 using deionised water and seawater as leaching solutions. The experimental conditions mimic different circumstances of the marine environment due to the global acidification, carbon dioxide (CO2) leakages from carbon capture and sequestration technologies, and accidental chemical spills in seawater. Leaching test results using seawater as leaching solution show a better neutralisation capacity giving slightly lower metal leaching concentrations than when using deionised water. The contaminated sediment shows a low base-neutralisation capacity (BNCpH 12 = -0.44 eq/kg for deionised water and BNCpH 12 = -1.38 eq/kg for seawater) but a high acid-neutralisation capacity when using deionised water (ANCpH 4 = 3.58 eq/kg) and seawater (ANCpH 4 = 3.97 eq/kg). Experimental results are modelled with the Visual MINTEQ geochemical software to predict metal release from sediment using both leaching liquids. Surface adsorption to iron- and aluminium-(hydr)oxides was applied for all studied elements. The consideration of the metal-organic matter binding through the NICA-Donnan model and Stockholm Humic Model for lead and copper, respectively, improves the former metal release prediction. Modelled curves can be useful for the environmental impact assessment of seawater acidification due to its match with the experimental values.

Evaluation through column leaching tests of metal release from contaminated estuarine sediment subject to CO2 leakages from Carbon Capture and Storage sites.

The pH change and the release of organic matter and metals from sediment, due to the potential CO(2) acidified seawater leakages from a CCS (Carbon Capture and Storage) site are presented. Column leaching test is used to simulate a scenario where a flow of acidified seawater is in contact with recent contaminated sediment. The behavior of pH, dissolved organic carbon (DOC) and metals As, Cd, Cr, Cu, Ni, Pb, Zn, with liquid to solid (L/S) ratio and pH is analyzed. A stepwise strategy using empirical expressions and a geochemical model was conducted to fit experimental release concentrations. Despite the neutralization capacity of the seawater-carbonate rich sediment system, important acidification and releases are expected at local scale at lower pH. The obtained results would be relevant as a line of evidence input of CCS risk assessment, in an International context where strategies to mitigate the climate change would be applied.

Study of the delignification of hardwood chips in a pulping process for sugar production.

Spent sulphite liquor is a lignocellulosic residue obtained in the acid sulphite pulping process after the digestion of hardwood chips, and composed mainly by lignosulphonates and hemicelluloses. The aim of this work is to study the main process variables at different digestion conditions: maximum temperature, heating rate, and total SO2 content, which affect the delignification process of hardwood chips to obtain dissolving pulp and to increase the total amount of fermentable sugars and lignosulphonates presented in this lignocellulosic waste. The best results are 210.5 g/L of lignosulphonates and 47.26 g/L of total monosaccharides obtained at higher temperatures of 1.058T and 1.072T, low heating rates of 0.334R and 0.285R, and total SO2 content of 6.20%. Furthermore, concentrate-acid hydrolysis of the liquor with sulphuric acid was performed in order to study the evolution of the sugar content and the release of the inhibitors. Temperature, acid concentration, acid/liquor ratio and time were modified, showing that acid/liquid ratio is the most influential variable. Although increase in the content of sugars in neither case, a notable furfural and acetic acid concentration decrease is registered, 97.88% and 36.57% respectively, at 20 °C, 60% (w/w) sulphuric acid and acid/sample ratio of 1/0.1 (v/v).

Potential influence of CO2 release from a carbon capture storage site on release of trace metals from marine sediment.

One of the main risks of CCS (Carbon Capture and Storage) is CO(2) leakage from a storage site. The influence of CO(2) leakage on trace metals leaching from contaminated marine sediment in a potential storage area (Northern Spain) is addressed using standardized leaching tests. The influence of the pH of the leaching solution on the leachates is evaluated using deionized water, natural seawater and acidified seawater at pH = 5, 6 and 7, obtained by CO(2) bubbling. Equilibrium leaching tests (EN 12457) were performed at different liquid-solid ratios and the results of ANC/BNC leaching test (CEN/TS 15364) were modeled using Visual Minteq. Equilibrium tests gave values of the final pH for all seawater leachates between 7 and 8 due to the high acid neutralization capacity of the sediment. Combining leaching test results and geochemical modeling provided insight in the mechanisms and prediction of trace metals leaching in acidified seawater environment.

Biomarker responsiveness in different tissues of caged Ruditapes philippinarum and its use within an integrated sediment quality assessment.

Biomarkers comprising activities of biotransformation enzymes (ethoxyresorufin-O-deethylase -EROD-, dibenzylfluorescein dealkylase -DBF-, glutathione S-transferase -GST), antioxidant enzymes (glutathione reductase -GR- and glutathione peroxidase -GPX), lipid peroxidation -LPO- and DNA strand breaks were analyzed in the clam Ruditapes philippinarum caged at Cádiz Bay, Santander Bay and Las Palmas de Gran Canaria (LPGC) Port (Spain). Sediments were characterized. Digestive gland was the most sensitive tissue to sediment contamination. In Cádiz Bay, changes in LPO regarding day 0 were related with metals. In LPGC Port, DBF, EROD, and GST activity responses suggested the presence of undetermined contaminants which might have led to DNA damage. In Santander Bay, PAHs were related with EROD activity, organic and metal contamination was found to be associated with GR and GST activities and DNA damage presented significant (p < 0.05) induction. R. philippinarum was sensitive to sediment contamination at biochemical level. Biomarkers allowed chemical exposure and sediment quality assessment.

Influence of the organic compounds on the ecotoxicity in the treatment of foundry sludge and olive mill waste.

The study of the ecotoxicity in two industrial waste materials and the relationships with the organic parameters has been conducted. Foundry sludge and olive mill waste have been used as industrial waste materials with organic or mixed character. Stabilisation/solidification (S/S) and advanced oxidation (AOP) processes have been carried out in order to treat both foundry sludge and olive mill waste. Analysis of ecotoxicity, total organic carbon, COD and phenol index have been evaluated in the untreated waste and end-products. The results of the treated samples allow obtaining the best formulations in both processes. The best formulations in the immobilisation process have been obtained with Portland cement and black carbon, activated carbon or foundry sand ashes. In the AOP process, ozone concentrations above 35 mg/l and reaction times equal to 120 minutes have been the optimal variables. The relationships between the organic parameters and the ecotoxicity of the samples have been studied in this paper. Furthermore, the global organic parameters have been studied in relation to the phenolic compounds. Lineal and logarithmic expressions have been obtained between the total organic carbon and phenol index and the ecotoxicity of the samples related to the organic parameters, respectively. Ecotoxicity of the samples with Vibrio fischeri is recommended as a very promising biotest for the study of the characterisation and the evaluation of the treatment of organic and mixed character waste and total organic carbon is recommended as global organic parameter in the treatment of foundry sludge.

Electrochemical treatment of textile dyes and dyehouse effluents.

The electrochemical oxidation of textile effluents over a titanium-tantalum-platinum-iridium anode was investigated. Batch experiments were conducted in a flow-through electrolytic cell with internal recirculation at current intensities of 5, 10, 14 and 20A, NaCl concentrations of 0.5, 1, 2 and 4% and recirculation rates of 0.81 and 0.65 L/s using a highly colored, synthetic effluent containing 16 textile dyes at a total concentration of 361 mg/L and chemical oxygen demand (COD) of 281 mg/L. Moreover, an actual dyehouse effluent containing residual dyes as well as various inorganic and organic compounds with a COD of 404 mg/L was tested. In most cases, quantitative effluent decolorization was achieved after 10-15 min of treatment and this required low energy consumption; conversely, the extent of mineralization varied between 30 and 90% after 180 min depending on the operating conditions and the type of effluent. In general, treatment performance improved with increasing current intensity and salinity and decreasing solution pH. However, the use of electrolytes not containing chloride (e.g. FeSO4 or Na2SO4) suppressed degradation. Although the acute toxicity of the actual effluent to marine bacteria Vibrio fischeri was weak, it increased sharply following treatment, thus suggesting the formation of persistent toxic by-products.

Environmental behaviour of stabilised foundry sludge.

Environmental characterisation of foundry sludge (FS) and the stabilised/solidified (S/S) derived products has been performed according to the leaching behaviour. Portland cement and lime have been used as binders and foundry sand fines, activated carbon and black carbon have been used as additives in the S/S processes. The results of the characterisation show that the behaviour of the waste in acid media is mainly influenced by the inorganic components of the waste, while the organic matter only has an influence in the redox potential of the leachates. Due to the complexity of the waste, a computer modelling of equilibrium (MINTEQ) has been used in order to compare the experimental extractability with the simulated curves of the metallic species. The zinc content in the leachate is close related to the theoretical curves in the waste and all S/S products, while the rest of the metals do not show a coherent behaviour with the hydroxides evolution. The results of compliance testing allow to obtain the best S/S formulations using activated and black carbon as sorbents. The comparison between different leaching procedures leads to equivalent results depending only on the pH.

Ecotoxicity assessment of stabilized/solidified foundry sludge.

The aim of this study is to evaluate the toxicity of the leachates from a foundry sludge and the derived products based on the stabilization/solidification (S/S) processes. Foundry sludge is an industrial hazardous waste containing inorganic and organic pollutants. The immobilization of the foundry waste has been performed using different S/S procedures based on cement or lime as binder agents and foundry sand fines, calcium-magnesium lignosulfonate, silica fume, activated carbon and black carbon as additives. The waste and stabilized/solidified derived products have been evaluated according to environmental considerations. The relation between the chemical composition and the ecotoxicity of the leachates has been studied in this paper. The ecotoxicity of the leachates has been related to the heavy metals and the organic pollutants by an empirical logarithmic linear expression. Different parameters of the logarithmic fitting have been obtained for the studied binder agents and additives allowing the establishment of a relationship between the S/S process and the ecotoxicity of the derived products. Results of this study have wide-ranging implications for immediate management strategies of waste with organic and inorganic pollutants in addition to application in long-term remediation efforts.