Sustain. Chem., Volume 1, Issue 2 (September 2020) – 7 articles

Fossil fuel refining produces over 70 Mt of excess sulfur annually from for which there is currently no practical use. Recently, methods to convert waste sulfur to recyclable and biodegradable polymers have been delineated. In this report, a commercial bisphenol A (BPA) derivative, 2,2′,5,5′-tetrabromo(bisphenol A) (Br₄BPA), is explored as a potential organic monomer for copolymerization with elemental sulfur by RASP (radical-induced aryl halide-sulfur polymerization). Resultant copolymers, BAS_x (x = wt% sulfur in the monomer feed, screened for values of 80, 85, 90, and 95) were characterized by thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis. Analysis of early stage reaction products and depolymerization products support proposed S–C_aryl bond formation and regiochemistry, while fractionation of BAS_x reveals a sulfur rank of 3–6. Copolymers having less organic cross-linker (5 or 10 wt%) in the monomer feed were thermoplastics, whereas thermosets were accomplished when 15 or 20 wt% of organic cross-linker was used. The flexural strengths of the thermally processable samples (>3.4 MPa and >4.7 for BAS₉₅ and BAS₉₀, respectively) were quite high compared to those of familiar building materials such as portland cement (3.7 MPa). Furthermore, copolymer BAS₉₀ proved quite resistant to degradation by oxidizing organic acid, maintaining its full flexural strength after soaking in 0.5 M H₂SO₄ for 24 h. BAS₉₀ could also be remelted and recast into shapes over many cycles without any loss of mechanical strength. This study on the effect of monomer ratio on properties of materials prepared by RASP of small molecular aryl halides confirms that highly cross-linked materials with varying physical and mechanical properties can be accessed by this protocol. This work is also an important step towards potentially upcycling BPA from plastic degradation and sulfur from fossil fuel refining. Full article

Rapid urbanization, advancements in science and technology, and the increase in tech-savviness of consumers have led to an exponential production of a variety of electronic equipment. The global annual growth rate of e-waste volume exceeds the growth rate of the human population. Electronic waste has now become a point of concern globally (53.6 million metric tons, 2019). However, merely 17.4% of all global e-waste is properly collected and recycled. China is the largest contributor to the global production of e-waste (~19%), the second being the United States. Indeed, only 14 countries generated over 65% of global e-waste production in 2019. E-wastes contain a wide range of organic, and inorganic compounds including various metals. Emerging contaminants like plastics are amongst the fastest growing constituents of electronic waste. The current challenges include the lack of reliable data, inadequate identification and quantification of new emerging materials, limited effectiveness of current recycling technologies, need for cutting-edge detection and recycling technologies, and the lack of e-waste management policies and international collaboration. In this review, we strive to integrate the existing data on production rates at different spatial scales, composition, as well as health, economical, and environmental challenges, existing recycling technologies; explore tangible solutions; and encourage further sustainable technology and regulatory policies. Full article

Two catalysts are prepared by tethering ionic liquid cation components (1-(propyl-3-sulfonate)-3-(3-trimethoxysilylpropyl) imidazolium) with either chloride or sulphate anions, to the surface of a mesoporous SiO₂ material through a condensation reaction. These are characterized using elemental analysis, TGA-MS, FTIR (and D-FTIR), TEM, physisorption and NH₃ adsorption (TPD and FTIR), and applied in the valeric acid + pentanol esterification reaction to form the sustainable biodiesel Pentyl Valerate. The material containing the sulfate counter-ion was significantly more active than the chloride analogue. Full article

Throughout numerous research works on biomacromolecules, several breakthrough innovations have occurred in the field of biomacromolecule processing. Remarkable improvements have been made so far to address the problems associated with biomacromolecule processing technologies in terms of enhancing the efficiency of the processes. Green technology broadly focuses on the search for new techno-economic systems to replace the conventional systems which exhibit pernicious consequences for the environment and the health of organisms. The strategy practiced popularly is the use of alternate solvent systems, replacing the conventional toxic, volatile, and harsh organic solvents to prevent denaturation, biotransformation, enzyme activity loss, and degradation of biomacromolecules. Ionic liquids (ILs) and deep eutectic solvents (DESs) are emerging as greener alternatives over the past two decades and there has been an exponential increase in reports in the literature. The utility of neoteric solvents in biomacromolecule treatment may be envisaged for industrial processes in the near future. The current state of the art regarding the recent developments made over the past few years using neoteric solvents has been reviewed in this article. The recent scientific developments regarding the use of these neoteric solvents, especially ILs and DESs, for processes such as solubilization, extraction, and functionalization of biomacromolecules, especially proteins and DNA, have been addressed in this article. This review may be beneficial for designing novel and selective methodologies for the processing of biomacromolecules, opening doors for better material research in areas such as biotechnology and biological sciences. Full article

Waste lignocellulosic biomass is sustainable and an alternative feedstock to fossil resources. Among the lignocellulosic derived compounds, 2,5-dimethylfuran (DMF) is a promising building block for chemicals, e.g., p-xylene, and a valuable biofuel. DMF can be obtained from 5-hydroxymethylfurfural (HMF) via catalytic deoxygenation using non-noble metals such as Ni in the presence of H₂. Herein, we present the synthesis of DMF from HMF using 35 wt.% Ni on nitrogen-doped carbon pellets (35Ni/NDC) as a catalyst in a continuous flow system. The conversion of HMF to DMF was studied at different hydrogen pressures, reaction temperatures, and space times. At the best reaction conditions, i.e., 423 K, 8.0 MPa, and space time 6.4 kg_Ni h kg_HMF⁻¹, the 35Ni/NDC catalyst exhibited high catalytic activity with HMF conversion of 99 mol% and 80 mol% of DMF. These findings can potentially contribute to the transition toward the production of sustainable fine chemicals and liquid transportation fuels. Full article

Tungsten carbide (WC) nanostructures were prepared by carbothermal reduction (CR) of tungsten-impregnated pinewood-derived activated carbon (AC) at 1000 °C under an inert atmosphere. Brunauer-Emmet-Teller (BET) surface area, pore structures of the AC, and catalyst samples were evaluated by N₂ adsorption-desorption experiments. The structures of the catalysts were characterized using X-ray powder diffraction (XRD). The morphologies and particle structures of the synthesized WC nanoparticles were investigated by field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM). The WC/AC material was used as support of the platinum catalysts for catalytic oxidation of formaldehyde (HCHO) from interior sources. Pt-WC/AC catalysts with different platinum loadings were assessed for the catalytic oxidation of HCHO at low temperature. The catalytic performance was found to be significantly influenced by reaction temperature, initial formaldehyde concentration, relative humidity, and space velocity. The testing results demonstrated that HCHO can be totally oxidized by the 1 wt% Pt-WC/AC catalyst in the gas hourly space velocity (GHSV) = 50,000 h⁻¹ at 30 °C with a relative humidity (RH) of 40%. Full article

Lignocellulosic biomass (LB) is recalcitrant to enzymatic hydrolysis due to its compact and complex cell wall structure. To identify the parameters behind LB recalcitrance, experimental data over hydrolysis time must be collected. Here, we describe a novel method to collect time-lapse images during cell wall deconstruction by enzymatic hydrolysis. The protocol includes instructions for sample preparation, layout of a custom designed incubation chamber and instructions for confocal time lapse acquisition. The protocol sets out a detailed plan where cross-sections of untreated and pretreated poplar samples are mounted in a sealed frame containing a buffer and an enzymatic cocktail. The sealed frame is then placed into an incubator to maintain the sample at a constant temperature of 50 °C, which is optimal for enzymatic reaction while avoiding enzymatic cocktail evaporation. Using lignin natural autofluorescence, confocal z-stacks of untreated and pretreated samples were acquired at regular time intervals during enzymatic hydrolysis for 24 h. Acquisition parameters were optimized to compromise between image resolution and reduced photo-bleaching. The acquired image might then be processed by further development of algorithms to extract precise quantitative information on cell wall deconstruction. This protocol is an important first step towards elucidating the underlying parameters of LB recalcitrance by allowing the acquisition of high-quality images of LB hydrolysis for extracting quantitative data on LB deconstruction. Full article