Research on using biochar for environmental applications has witnessed unprecedented advances in the past decade. Biochar is universally considered one of the best alternatives to store carbon to fight global warming. Thus, the sequential use of biochar in environmental remediation compatible with carbon sequestration is receiving growing attention. One of the reasons for such huge interest is the possibility to engineer biochar with targeted properties (e.g., surface area and chemistry) relevant to existing environmental issues. These properties can be achieved by selecting appropriate raw materials, processing conditions, carbonization technology, and the possibility of selecting postproduction modification approaches. The objective of this review is to summarize strategies to enhance biochar properties relevant to its use in environmental services (e.g., water purification, air/gas cleaning, construction materials, soil amendments) and the corresponding results on the use of this material for these applications. The main methods for enhancing biochar properties for environmental applications reviewed include activation (physical and chemical), oxidation, metal and metal oxide modification, metal-free heteroatom doping, and biological modification. Both modified and unmodified biochars have been used for soil amendments as adsorbents of pollutants in the aqueous phase (e.g., removal of P and N, heavy metals, and organic pollutants), adsorbents of pollutants in the gas phase (e.g., biogas cleaning), as a catalyst, as an additive for improving anaerobic digestion, and as an admixture to cementitious/construction materials, with promising results in all cases. New opportunities for using biochar are being reported as the science of biochar production, modification, and use advances. 

Perspectives of Engineered Biochar for Environmental Applications: A Review

Measurement of non-hindered and hindered phenolic species in aviation fuels via tandem-SPE with comprehensive GC × GC–MS/FID

Many scientists are increasingly interested in on-site detection methods of phenol and its derivatives because these substances have been universally used as a significant raw material in the industrial manufacturing of various chemicals of antimicrobials, anti-inflammatory drugs, antioxidants, and so on. The contamination of phenolic compounds in the natural environment is a toxic response that induces harsh impacts on plants, animals, and human health. This mini-review updates recent developments and trends of novel plasmonic resonance nanomaterials, which are assisted by various optical sensors, including colorimetric, fluorescence, localized surface plasmon resonance (LSPR), and plasmon-enhanced Raman spectroscopy. These advanced and powerful analytical tools exhibit potential application for ultrahigh sensitivity, selectivity, and rapid detection of phenol and its derivatives. In this report, we mainly emphasize the recent progress and novel trends in the optical sensors of phenolic compounds. The applications of Raman technologies based on pure noble metals, hybrid nanomaterials, and metal–organic frameworks (MOFs) are presented, in which the remaining establishments and challenges are discussed and summarized to inspire the future improvement of scientific optical sensors into easy-to-operate effective platforms for the rapid and trace detection of phenol and its derivatives.

Recent Developments in Plasmonic Sensors of Phenol and Its Derivatives

Highly sensitive solid-state fluorescent sensor immobilized on silica nanoparticles for direct detection dimethyl phenol in seawater samples

http://manuscript.elsevier.com/S0959652622008538/pdf/S0959652622008538.pdf

Wet oxidation of thermochemical aqueous effluent utilizing char catalysts in microreactors

Identification and quantification of trace oxygenated compounds in alternative jet fuels: Fluorescence methods for fast detection of phenolic compounds in operational field conditions

Catalytic wet oxidation (CWO) of aqueous effluents rich in organic compounds is a very promising technology for the treatment of liquid wastes from biomass conversion processes. CWO reactions occur through the formation of free radical species, produced in the presence of an oxidant, which act on organic contaminates in the effluent. Although the reaction is well known, there exists a lack of affordable catalysts to conduct this process at the lower temperatures and pressures in novel bioenergy processes. This study assessed the catalytic effect of nitrogen-doped chars as such an option. Phenol in aqueous solution was used as a model waste effluent. Treatment was conducted at moderate temperatures (190 to 260 °C), oxygen partial pressure of 1 MPa, and reaction times of 15, 30, and 45 min in stainless steel and glass-lined tube reactors. High pressure liquid chromatography (HPLC) analyses of the products quantified phenol and by-product concentrations used in the calculation of reaction activation energy. The char catalyst was studied by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) in order to gain insight into its structure and surface composition. The results indicate that nitrogen-doped char catalysts accelerate the oxidation of phenol by decreasing its reaction activation energy from 82.2 kJ/mol (non-catalyzed) to 40.4 kJ/mol (catalyzed). An analysis from first principles using density functional theory (DFT) was conducted to ascertain which N functional group has the most significant impact on free radical formation in the presence of oxygen. Among all the N functional groups studied, the dipyridinic functional groups showed the most promising characteristics to facilitate the formation of hydroxyl free radicals.

Nitrogen-doped char as a catalyst for wet oxidation of phenol-contaminated water

Sustainable economic and industrial growth requires safe, sustainable resources of energy. Biofuel is becoming increasingly important as an alternative fuel for the diesel engine. The use of non-edible vegetable oils for biofuel production is significant because of the increasing demand for edible oils as food. With the recent debate of food versus fuel, some non-edible oils like soapnut and Jatropha (Jatropha curcus. L) are being investigated as possible sources of biofuel. Recent research has focused on the application of heterogeneous catalysis. This review considers catalytic transesterification and the possibility of heterogeneous base catalysts. The process of transesterification, and the effect of parameters, mechanism and kinetics are reviewed. Although chromatography (GC and HPLC) are the analytical methods most often used for biofuel characterization, other techniques and some improvements to analytical methods are discussed.

https://journals.sagepub.com/doi/pdf/10.3184/003685011X13205103999987

Kalidas Mainali

Papers

Identification and quantification of trace oxygenated compounds in alternative jet fuels: Fluorescence methods for fast detection of phenolic compounds in operational field conditions

Nitrogen-doped char as a catalyst for wet oxidation of phenol-contaminated water

Base catalytic transesterification of vegetable oil