Journal of Chemical Technology and Biotechnology

Microplastics are emerging persistent pollutants that have been extensively detected in aqueous environments. Yet, scientists have little knowledge of microplastic pollution in soils. This study reviewed over 60 articles, with the following objectives: (i) to discuss sources and the global distribution of microplastics in soils; (ii) to evaluate current extraction techniques and analytical methods for microplastics in soils; and (iii) to comprehensively assess their adverse impacts on soils and soil organisms. Moreover, this review highlights the lack of research into microplastic contamination in soils as a significant knowledge gap. Research into the fate, sources and analytical techniques of soil microplastics and the interactions between soil organisms, soils and microplastics is essential in order to underpin management decisions aimed at safeguarding the ecological integrity of our soils. © 2020 Society of Chemical Industry

Polycyclic aromatic hydrocarbons (PAHs) are a class of organic compounds that have accumulated in the natural environment mainly as a result of anthropogenic activities such as the combustion of fossil fuels. Interest has surrounded the occurrence and distribution of PAHs for many decades due to their potentially harmful effects to human health. This concern has prompted researchers to address ways to detoxify/remove these organic compounds from the natural environment. Bioremediation is one approach that has been used to remediate contaminated land and waters, and promotes the natural attenuation of the contaminants using the in situ microbial community of the site. This review discusses the variety of fungi and bacteria that are capable of these transformations, describes the major aerobic and anaerobic breakdown pathways, and highlights some of the bioremediation technologies that are currently available. Copyright © 2005 Society of Chemical Industry

BACKGROUND: Aqueous phase Fischer–Tropsch (FT) effluents co‐produced with hydrocarbons in the FT process contain various water‐soluble oxygenates, e.g. carboxylic acids, alcohols. Purification of the FT aqueous phase is important from the viewpoint of effective resource utilization and environmental stewardship. In this work, an aqueous‐phase hydrodeoxygenation process was investigated for the degradation of FT aqueous phases.

RESULTS: The Ru/AC catalyst was determined to be the most active catalyst. The key parameters, i.e. temperature, pressure, weight hourly space velocity and Ru loading, were comprehensively optimized. Under optimal conditions, ca 98% of the oxygenates were converted to C₁∼C₆ alkanes. The degraded water had no odour, a neutral pH, and as low as 1000 mg L⁻¹ chemical oxygen demand. The Ru/AC catalyst exhibited long‐term stability (1300 h) and no ruthenium leaching. A reaction pathway is proposed for this process in which the carboxylic acids are hydrogenated to alcohols via the formation of aldehydes. Alcohols and aldehydes are then converted to methane and alkanes of one carbon atom less than the substrate through CC bond cleavage.

CONCLUSIONS: This process is effective for treating FT aqueous phase effluent, and holds great promise for industrial applications due to its high efficiency, simplicity and stability. Copyright © 2011 Society of Chemical Industry

BACKGROUND: The catalytic degradation of aqueous Fischer–Tropsch (FT) effluents to fuel gas over Ru/AC has been investigated. In order to understand the catalytic performance and stability of oxide‐supported Ru catalysts, several oxide supports (titania, zirconia, γ‐alumina and silica) were selected for study, with a focus on the hydrothermal stability of catalysts.

RESULTS: The catalytic efficiency for transforming the oxygenates in aqueous FT effluents to C₁–C₆ alkanes decreased in the order: Ru/ZrO₂∼ Ru/TiO₂ > Ru/SiO₂ > Ru/Al₂O₃. The conversion of alcohols was greatly suppressed over Ru/γ‐Al₂O₃. The former two catalysts (Ru/ZrO₂ and Ru/TiO₂) exhibited enhanced efficiency and long‐term stability (400 h) relative to Ru/SiO₂ and Ru/Al₂O₃. N₂‐physisorption, XRD and SEM showed that titania and zirconia exhibited high structural stability in an aqueous environment. However, the structures of γ‐alumina and silica were unstable due to significant drop in surface area and adverse changes in surface morphology. Especially for the case of the Ru/γ‐Al₂O₃ catalyst, the γ‐alumina was transformed into boehmite structure after reaction, and metal leaching and carbon deposition were extensive.

CONCLUSION: Ru/ZrO₂ or Ru/TiO₂ may be a promising alternative for degrading aqueous FT effluents due to their long‐term stability. Copyright © 2012 Society of Chemical Industry

The effect of rapid mixing on floc formation, breakage and re‐formation using aluminium sulfate (‘alum’), polyaluminium chloride and a cationic polyelectrolyte were investigated using a continuous optical monitoring technique. For the aluminium‐based coagulants it was found that, with shorter times of rapid mix, larger flocs were formed, but only limited re‐growth occurred in all cases, indicating a significant irreversibility of the floc break‐up process. For cationic polyelectrolytes, the re‐growth of flocs occurred to a much greater extent and with longer rapid mix times floc breakage was almost fully reversible. Residual turbidity values before floc breakage and after re‐formation were consistent with the dynamic monitoring results. Copyright © 2004 Society of Chemical Industry

BACKGROUND: Currently, cellulose membranes are prepared by cellulose acetate hydrolysis or chemical derivatization dissolution and regeneration using cotton pulp or wood pulp. In this study, the concept ‘lignocelluloses biorefinery’ was used, and good quality long fiber was fractionated from wheat straw using clean technologies. The objective of this study is to develop wheat straw cellulose to prepare regenerated cellulose membrane with ionic liquid 1‐butyl‐3‐methylimidazolium chloride ([BMIM]Cl) as solvent.

RESULTS: Wheat straw cellulose (WSC) fractionated from wheat straw contained 93.6% α‐cellulose and the degree of polymerization (DP) was 580. WSC was dissolved directly without derivatization in [BMIM]Cl. With increase in dissolving temperature, the DP of the regenerated cellulose dropped, which resulted in a decrease in the intensity of regenerated cellulose membrane. After regeneration in [BMIM]Cl, the WSC transformed from cellulose I to cellulose II, and the crystallinity of the regenerated cellulose was lower than the original cellulose. The regenerated WSC membrane had good mechanical performance and permeability, the tensile strength and breaking elongation were 170 MPa and 6.4%, respectively, the pure water flux was 238.9 L m⁻² h⁻¹ at 0.3 MPa pressure, and the rejection of BSA was stabilized at about 97%.

CONCLUSION: Wheat straw cellulose fractionated from wheat straw satisfied the requirement to prepare regenerated cellulose membrane using ionic liquid [BMIM]Cl as solvent. Copyright © 2012 Society of Chemical Industry

CO₂is considered to play a key role in an eventual climate change, due to its accumulation in the atmosphere. The control of its emission represents a challenging task that requires new ideas and new technologies. The use of perennial energy sources and renewable fuels instead of fossil fuels and the conversion ofCO₂into useful products are receiving increased attention. The utilization ofCO₂as a raw material for the synthesis of chemicals and fuels is an area in which scientists and industrialists are much involved: the implementation of such technology on a large scale would allow a change from a linear use of fossil carbon to its cyclic use, mimicking Nature. In this paper the use ofCO₂as building block is discussed.CO₂can replace toxic species such as phosgene in low energy processes, or can be used as source of carbon for the synthesis of energy products. The reactions with dihydrogen, alcohols, epoxides, amines, olefins, dienes, and other unsaturated hydrocarbons are discussed, under various reaction conditions, using metal systems or enzymes as catalysts. The formation of products such as formic acid and its esters, formamides, methanol, dimethyl carbonate, alkylene carbonates, carbamic acid esters, lactones, carboxylic acids, and polycarbonates, is described.

The factors that have limited so far the conversion of large volumes ofCO₂are analyzed and options for large‐scaleCO₂catalytic conversion into chemicals and fuels are discussed. Both homogeneous and heterogeneous catalysts are considered and the pros and cons of their use highlighted. © 2013 Society of Chemical Industry