### Aug 2017, Volume 11 Issue 3

Cover illustration

• The authors of Special Topic on environment and sustainable development come from China, USA, Canada, Italia, the Netherlands and Belgium, thereby forming a union of chemical engineering from China, Europe, and North America.

• Select all
• Preface
• VIEWS & COMMENTS
David T. Allen

In Houston, a combination of urban emissions from a city of 4 million people, coupled with emissions from extensive petroleum refining and chemical manufacturing, leads to conditions for photochemistry that are unique in the United States, and historically, the city had experienced some of the highest ozone concentrations recorded in the United States. Large air quality field studies (the Texas Air Quality Studies or TexAQS I and II) were conducted to determine root causes of the high ozone concentrations. Hundreds of air quality investigators, from around the world, deployed instruments on aircraft, on ships, and at fixed ground sites to make extensive air quality measurements; detailed photochemical modeling was used to interpret and assess the implications of the measurements. The Texas Air Quality Studies revealed that both continuous and episodic emissions of light alkenes, which came to be called highly reactive volatile organic compounds, played a critical role in the formation of ozone and other photochemical oxidants in the region. Understanding and quantifying the role of these emissions in regional air quality required innovations in characterizing emissions and in photochemical modeling. Reducing emissions required innovative policy approaches. These coupled scientific and policy innovations are described, and the result, substantially cleaner air for Houston, is documented. The lessons learned from the Houston air quality experience are relevant to cities with similar population and industrial profiles around the world.

• VIEWS & COMMENTS
Zhongming Lu, Duo Li, John C. Crittenden
• RESEARCH ARTICLE
Zhi Sun, Hongbin Cao, Prakash Venkatesan, Wei Jin, Yanping Xiao, Jilt Sietsma, Yongxiang Yang

Leaching selectivity during metal recovery from complex electronic waste using a hydrochemical process is always one of the generic issues. It was recently improved by using ammonia-based leaching process, specifically for electronic waste enriched with copper. This research proposes electrodeposition as the subsequent approach to effectively recover copper from the solutions after selective leaching of the electronic waste and focuses on recognising the electrochemical features of copper recovery. The electrochemical reactions were investigated by considering the effects of copper concentration, scan rate and ammonium salts. The diffusion coefficient, charge transfer coefficient and heterogeneous reaction constant of the electrodeposition process were evaluated in accordance with different solution conditions. The results have shown that electrochemical recovery of copper from ammonia-based solution under the conditions of selective electronic waste treatment is charge transfer controlled and provide bases to correlate the kinetic parameters with further optimisation of the selective recovery of metals from electronic waste.

• RESEARCH ARTICLE
Remus I. Iacobescu, Valérie Cappuyns, Tinne Geens, Lubica Kriskova, Silviana Onisei, Peter T. Jones, Yiannis Pontikes

This study reports on the impact of the curing conditions on the mechanical properties and leaching of inorganic polymer (IP) mortars made from a water quenched fayalitic slag. Three similar IP mortars were produced by mixing together slag, aggregate and activating solution, and cured in three different environments for 28 d: a) at 20 °C and relative humidity (RH) ~ 50% (T20RH50), b) at 20 °C and RH≥90% (T20RH90) and c) at 60 °C and RH ~ 20% (T60RH20). Compressive strength (EN 196-1) varied between 19 MPa (T20RH50) and 31 MPa (T20RH90). This was found to be attributed to the cracks formed upon curing. Geochemical modelling and two leaching tests were performed, the EA NEN 7375 tank test, and the BS EN 12457-1 single batch test. Results show that Cu, Ni, Pb, Zn and As leaching occurred even at high pH, which varied between 10 and 11 in the tank test’s leachates and between 12 and 12.5 in the single batch’s leachates. Leaching values obtained were below the requirements for non-shaped materials of Flemish legislation for As, Cu and Ni in the single batch test.

• RESEARCH ARTICLE
Min Song, Wei Zhang, Yongsheng Chen, Jinming Luo, John C. Crittenden

Two types of lignin-based carbon fibers were prepared by electrospinning method. The first was activated with Fe3O4 (LCF-Fe), and the second was not activated with Fe3O4 (LCF). Gas phase adsorption isotherms for toluene on LCF-Fe and LCF were studied. The gas phase adsorption isotherm for 0% RH showed LCF-Fe have about 439 mg/g adsorption capacity which was close to that of commercially available activated carbon (500 mg/g). The Dubinin-Radushkevich equation described the isotherm data very well. Competitive adsorption isotherms between water vapor and toluene were measured for their RH from 0 to 80%. The effect of humidity on toluene gas-phase adsorption was predicted by using the Okazaki et al. model. In addition, a constant pattern homogeneous surface diffusion model (CPHSDM) was used to predict the toluene breakthrough curve of continuous flow-packed columns containing LCF-Fe, and its capacity was 412 mg/g. Our study, which included material characterization, adsorption isotherms, kinetics, the impact of humidity and fixed bed performance modeling, demonstrated the suitability of lignin-based carbon fiber for volatile organic compound removal from gas streams.

• RESEARCH ARTICLE
Tao Lu, Qilei Zhang, Shanjing Yao

To increase the efficiency of dye removal from wastewater using mycelial pellets, a bubble column reactor with a simple structure was designed and efficiently used to remove dyes from solution containing dyes. The mycelial pellets were prepared by marine fungus Aspergillus niger ZJUBE-1. Eight dyes were tested as dye targets for the adsorption capacity of mycelial pellets and good removal results were obtained. Eriochrome black T was selected as a model dye for characterizing the adsorption processes in detail. The measurement results of Zeta potential and FT-IR analysis indicate that the electrostatic attraction may play a key role in the biosorption process. The bubble column reactor was utilized to study the batch dye-removal efficiency of mycelial pellets. A re-culture process between every two batches, which was under non-sterile condition, successfully enhanced the utilization of mycelium biomass. The dye removal rate is 96.4% after 12 h in the first batch and then decreases slowly in the following batches. This semi-continuous mode, which consists of commutative processes of dye-removal and re-culture, has some outstanding advantages, such as low power consumption, easy operation, high dye removal rate, and efficient biomass utilization.

• RESEARCH ARTICLE
Linghui Yu, Jiansong Miao, Yi Jin, Jerry Y.S. Lin

Coating commercial porous polyolefin separators with inorganic materials can improve the thermal stability of the polyolefin separators and hence improve the safety of lithium-ion batteries. Several different inorganic materials have been studied for the coating. However, there lacks a study on how different inorganic materials affect the properties of separators, in terms of thermal stability and cell performance. Herein, we present such a study on coating a commercial polypropylene separator with four inorganic materials, i.e., Al2O3, SiO2, ZrO2 and zeolite. All inorganic coatings have improved thermal stability of the separators although with differences. The coating layers add 28%–45% of electrical resistance compared with the pure polypropylene separator, but all the cells prepared with the coated polypropylene separators have the same electrical chemical performance as the uncoated separator in terms of rate capability and capacities at different temperatures.

• RESEARCH ARTICLE
Xuan Wang, Daneel Geysen, Tom Van Gerven, Peter T. Jones, Bart Blanpain, Muxing Guo

The slag samples taken from landfill, which originated from different metallurgical processes, have been characterized in this study. The slags were categorized as electric arc furnace (EAF) slag, argon oxygen decarburization/metal refining process slag and vacuum oxygen decarburization slag based on chromium content and basicity. EAF slags have higher potential in metal recovery than the other two slags due to its higher iron and chromium contents. The size of the iron-chromium-nickel alloy particles varies from a few µm up to several cm. The recoveries of large metal particles and metal-spinel aggregates have potential to make the metal recovery from landfilled slags economically viable.

• RESEARCH ARTICLE
Wen Zhao, Jiahua Xing, Tianming Xu, Weili Peng, Xinghai Liu

Pyrazole carboxamide derivatives represent an important class of fungicides in agrochemicals. To find more novel structural pyrazole carboxamides, a novel series of 3-(trifluoromethyl)-1H-pyrazole-4-carboxamide compounds were prepared from ethyl 4,4,4-trifluoroacetoacetate and triethyl orthoformate as starting materials. All the products were characterized by Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance (NMR), 13C NMR, 19F NMR and mass spectrography. The bioassay results showed these fluorine-containing pyrazole carboxamides have a weak fungicidal activity but some of them exhibit a good nematocidal activity against M. incognita.

• RESEARCH ARTICLE
Alexander B. Koven, Shitang S. Tong, Ramin R. Farnood, Charles Q. Jia

Generating hydrogen gas from biomass is one approach to lowering dependencies on fossil fuels for energy and chemical feedstock, as well as reducing greenhouse gas emissions. Using both equilibrium simulations and batch experiments with NaOH as a model alkaline, this study established the technical feasibility of converting various biomasses (e.g., glucose, cellulose, xylan and lignin) into H2-rich gas via catalyst-free, alkali-thermal gasification at moderate temperatures (as low as 300 °C). This process could produce more H2 with less carbon-containing gases in the product than other comparable methods. It was shown that alkali-thermal gasification follows$Cx HyOz+ 2xNaOH+(x−z)H2 O=$ $(2x+y/2−z )H2+x Na2 CO 3$, with carbonate being the solid product which is different from the one suggested in the literature. Moreover, the concept of hydrogen generation potential (H2-GP)—the maximum amount of H2 that a biomass can yield, was introduced. For a given biomass CxHyOz, the H2-GP would be  moles of H2. It was demonstrated experimentally that the H2- GP was achievable by adjusting the amounts of H2O and NaOH, temperature and pressure.

• RESEARCH ARTICLE
Xiaoming Ding, Zhiwen Zhai, Luping Lv, Zhaohui Sun, Xinghai Liu

A variety of pyrazole derivatives containing 1,3,4-thiadiazole moiety were synthesized under microwave irradiation, and their structures were confirmed by 1H NMR and HRMS. They were evaluated for herbicidal and antifungal activities, and the results indicated that two compounds with a phenyl group (6a) and 4-tert-butylphenyl group (6n) possess good herbicidal activity for dicotyledon Brassica campestris and Raphanus sativus with the inhibition of 90% for root and 80%–90% for stalk at 100 ppm respectively. The structure-activity relationship of compounds 6a and 6n was also studied by density function theory method.

• RESEARCH ARTICLE
Yu Yang, Hassan Javed, Danning Zhang, Deyi Li, Roopa Kamath, Kevin McVey, Kanwartej Sra, Pedro J.J. Alvarez

Heavy hydrocarbons (HHCs) in soils impacted by crude oil spills are generally recalcitrant to biodegradation due to their low bioavailability and complex chemical structure. In this study, soils were pretreated with varying concentrations of ultraviolet radiation A (UVA) or ultraviolet radiation C (UVC) activated titanium dioxide (TiO2) (1%–5%) under varying moisture conditions (0%–300% water holding capacity (WHC)) to enhance biodegradation of HCCs and shorten remediation timeframes. We demonstrate that pretreatment of impacted soils with UVC-activated TiO2 in soil slurries could enhance bioremediation of HHCs. ?Total petroleum hydrocarbon (TPH) removal after 24 h exposure to UVC (254 nm and 4.8 mW/cm2) was (19.1±1.6)% in slurries with 300% WHC and 5 wt-% TiO2. TPH removal was non-selective in the C15-C36 range and increased with moisture content and TiO2 concentration. In a 10-d bioremediation test, TPH removal in treated soil increased to (26.0±0.9)%, compared to (15.4±0.8)% for controls without photocatalytic pre-treatment. Enhanced biodegradation was also confirmed by respirometry. This suggests that addition of UVC-activated TiO2 to soil slurries can transform recalcitrant hydrocarbons into more bioavailable and biodegradable byproducts and increase the rate of subsequent biodegradation. However, similar results were not observed for soils pretreated with UVA activated TiO2. This suggests that activation of TiO2 by sunlight and direct addition of TiO2 to unsaturated soils within landfarming setting may not be a feasible approach. Nevertheless, less than 1% of UVA (7.5 mW/cm2) or UVC (1.4 mW/cm2) penetrated beyond 0.3 cm soil depth, indicating that limited light penetration through soil would hinder the ability of TiO2 to enhance soil bioremediation under land farming conditions.

• RESEARCH ARTICLE
Zijian Cui, Kaiyue Zhang, Guangyu Xing, Yaqing Feng, Shuxian Meng

Three-dimensional TiO2 microspheres doped with N were synthesized by a simple single-step solvothermal method and the sample treated for 15 h (hereafter called TMF) was then used as scattering layers in the photoanodes of dye-sensitized solar cells (DSSCs). The TMF was characterized using scanning electron microscopy, high resolution transmission electron microscopy, Brunauer-Emmett-Teller measurements, X-ray diffraction, and X-ray photoelectron spectroscopy. The TMF had a high surface area of 93.2 m2·g1 which was beneficial for more dye-loading. Five photoanode films with different internal structures were fabricated by printing different numbers of TMF scattering layers on fluorine-doped tin oxide glass. UV-vis diffuse reflection spectra, incident photon-to-current efficiencies, photocurrent-voltage curves and electrochemical impedance spectroscopy were used to investigate the optical and electrochemical properties of these photoanodes in DSSCs. The presence of nitrogen in the TMF changed the TMF microstructure, which led to a higher open circuit voltage and a longer electron lifetime. In addition, the presence of the nitrogen significantly improved the light utilization and photocurrent. The highest photoelectric conversion efficiency achieved was 8.08%, which is much higher than that derived from typical P25 nanoparticles (6.52%).

• RESEARCH ARTICLE
Matteo Minelli, Maria Grazia De Angelis, Giulio C. Sarti

The possibility to evaluate in a predictive way the relevant transport properties of low molecular weight species, both gases and vapors, in glassy polymeric membranes is inspected in detail, with particular attention to the methods recently developed based on solid thermodynamic basis. The solubility of pure and mixed gases, diffusivity and permeability of single gases in polymer glasses are examined, considering in particular poly(2,6-dimethyl-1,4-phenylene oxide) as a relevant test case. The procedure clearly indicates what are the relevant physical properties of the polymer matrix and of the penetrants required by the calculations, which can be obtained experimentally through independent measurements. For gas and vapor solubility, the comparison with direct experimental data for mixed gases points out also the ability to account for the significant variations that solubility-selectivity experiences upon variations of pressure and/or feed composition. For gas and vapor permeability, the comparison with direct experimental data shows the possibility to account for the various different trends observed experimentally as penetrant pressure is increased, including the so-called plasticization behavior. The procedure followed for permeability calculations leads also to clear correlations between permeability and physical properties of both polymer and penetrant, based on which pure predictive calculations are reliably made.

• RESEARCH ARTICLE
Weichao Yue, Xiaofang Chen, Weihua Gui, Yongfang Xie, Hongliang Zhang

Root cause analysis (RCA) of abnormal aluminum electrolysis cell condition has long been a challenging industrial issue due to its inherent complexity in analyzing based on multi-source knowledge. In addition, accurate RCA of abnormal aluminum electrolysis cell condition is the precondition of improving current efficiency. RCA of abnormal condition is a complex work of multi-source knowledge fusion, which is difficult to ensure the RCA accuracy of abnormal cell condition because of dwindling and frequent flow of experienced technicians. In view of this, a method based on Fuzzy-Bayesian network to construct multi-source knowledge solidification reasoning model is proposed. The method can effectively fuse and solidify the knowledge, which is used to analyze the cause of abnormal condition by technicians providing a clear and intuitive framework to this complex task, and also achieve the result of root cause automatically. The proposed method was verified under 20 sets of abnormal cell conditions, and implements root cause analysis by finding the abnormal state of root node, which has a maximum posterior probability by Bayesian diagnosis reasoning. The accuracy of the test results is up to 95%, which shows that the knowledge reasoning feasibility for RCA of aluminum electrolysis cell.

• RESEARCH ARTICLE
Xin Peng, Yang Tang, Wenli Du, Feng Qian

In this paper, we propose a novel performance monitoring and fault detection method, which is based on modified structure analysis and globality and locality preserving (MSAGL) projection, for non-Gaussian processes with multiple operation conditions. By using locality preserving projection to analyze the embedding geometrical manifold and extracting the non-Gaussian features by independent component analysis, MSAGL preserves both the global and local structures of the data simultaneously. Furthermore, the tradeoff parameter of MSAGL is tuned adaptively in order to find the projection direction optimal for revealing the hidden structural information. The validity and effectiveness of this approach are illustrated by applying the proposed technique to the Tennessee Eastman process simulation under multiple operation conditions. The results demonstrate the advantages of the proposed method over conventional eigendecomposition-based monitoring methods.

• RESEARCH ARTICLE
Yang Zhou, Phillip Choi

Isothermal-isobaric molecular dynamics simulation was used to study the diffusion mechanism of water in polyurethane-block-poly(N-isopropyl acrylamide) (PU-block-PNIPAm) with a hydrophobic PU/hydrophilic PNIPAm mass ratio of 1.4 to 1 at 298 K and 450 K. Here, the experimental glass transition temperature (Tg) of PU is 243 K while that of PNIPAm is 383 K. Different amounts of water up to 15 wt-% were added to PU-block-PNIPAm. We were able to reproduce the specific volumes and glass transition temperatures (250 K and 390 K) of PU-block-PNIPAm. The computed self-diffusion coefficient of water increased exponentially with increasing water concentration at both temperatures (i.e., following the free volume model of Fujita). It suggested that water diffusion in PU-block-PNIPAm depends only on its fractional free volume despite the free volume inhomogeneity. It is noted that at 298 K, PU is rubbery while PNIPAm is glassy. Regardless of temperature, radial distribution functions showed that water formed clusters with sizes in the range of 0.2–0.4 nm in PU-block-PNIPAm. At low water concentrations, more clusters were found in the PU domain but at high water concentrations, more in the PNIPAm domain. It is believed that water molecules diffuse as clusters rather than as individual molecules.

• REVIEW ARTICLE
Jumin Hao, Xiaoguang Meng

Perchlorate has recently emerged as a widespread environmental contaminant of healthy concern. Development of novel detection methods for perchlorate with the potential for field use has been an urgent need. The investigation has shown that surface-enhanced Raman scattering (SERS) technique has great potential to become a practical analysis tool for the rapid screening and routine monitoring of perchlorate in the field, particularly when coupled with portable/handheld Raman spectrometers. In this review article, we summarize progress made in SERS analysis of perchlorate in water and other media with an emphasis on the development of SERS substrates for perchlorate detection. The potential of this technique for fast screening and field testing of perchlorate-contaminated environmental samples is discussed. The challenges and possible solutions are also addressed, aiming to provide a better understanding on the development directions in the research field.

• REVIEW ARTICLE
Shoshan T. Abrahami, John M. M. de Kok, Herman Terryn, Johannes M. C. Mol

For more than six decades, chromic acid anodizing (CAA) has been the central process in the surface pre-treatment of aluminum for adhesively bonded aircraft structures. Unfortunately, this electrolyte contains hexavalent chromium (Cr(VI)), a compound known for its toxicity and carcinogenic properties. To comply with the new strict international regulations, the Cr(VI)-era will soon have to come to an end. Anodizing aluminum in acid electrolytes produces a self-ordered porous oxide layer. Although different acids can be used to create this type of structure, the excellent adhesion and corrosion resistance that is currently achieved by the complete Cr(VI)-based process is not easily matched. This paper provides a critical overview and appraisal of proposed alternatives to CAA, including combinations of multiple anodizing steps, pre- and post anodizing treatments. The work is presented in terms of the modifications to the oxide properties, such as morphological features (e.g., pore size, barrier layer thickness) and surface chemistry, in order to evaluate the link between fundamental principles of adhesion and bond performance.

• REVIEW ARTICLE
Brajendra Mishra, Sumedh Gostu

Bayer’s process revolutionized the extraction of aluminum from the bauxite ores. However, the hydrothermal extraction of alumina is associated with the generation of a byproduct, red-mud consisting of undissolved solids composed of iron oxides, sodium alumino silicates, titania, silica and rare earth elements. The accumulation of red-mud (or bauxite residue) in the world is 30 billion metric tons produced at a rate of 125 million tons per annum (2013). Utilization of red-mud for constructional purposes, wastewater treatment, metallurgical products, and pigments are listed. Metallurgical processing efforts of red-mud to generate various value added products such as pig iron, direct reduced iron slag wool, magnetite, titania, iron carbides are presented in the article.

• REVIEW ARTICLE
Kevin A. Kovalchik, Matthew S. MacLennan, Kerry M. Peru, John V. Headley, David D.Y. Chen

Naphthenic acids are a complex class of thousands of naturally occurring aliphatic and alicyclic carboxylic acids found in oil sands bitumen and in the wastewater generated from bitumen processing. Dozens of analytical methods have been developed for the semi-quantification of total naphthenic acids in water samples. However, different methods can give different results, prompting investigation into the comparability of the many methods. A review of important methodological features for analyzing total naphthenic acids is presented and informs the design of future standard methods for the semi-quantification of total naphthenic acids using mass spectrometry. The design considerations presented are a synthesis of discussions from an Environment and Climate Change Canada (ECCC) led taskforce of 10 laboratory experts from government, industry and academia during April 2016 and subsequent discussions between University of British Columbia and ECCC representatives. Matters considered are: extraction method, solvent, pH, and temperature; analysis instrumentation and resolution; choice of calibration standards; use of surrogate and internal standards; and use of online or offline separation prior to analysis. The design considerations are amenable to both time-of-flight and Orbitrap mass spectrometers.