Effect of Pyrolysis Temperature on PhysicoChemical Properties and Acoustic-Based Amination of Biochar for Efficient CO\u3csub\u3e2\u3c/sub\u3e Adsorption

© Copyright © 2020 Chatterjee, Sajjadi, Chen, Mattern, Hammer, Raman and Dorris. The present study examined the effect of pyrolysis temperature on the physicochemical properties of biochar, activation process and carbon capture. Two different categories of biochars were synthesized from herbaceous (miscanthus and switchgrass) and agro-industrial (corn stover and sugarcane bagasse) feedstock under four different pyrolysis temperatures −500, 600, 700, and 800°C. The synthesized biochars underwent sono-amination activation comprising low-frequency acoustic treatment followed by amine functionalization to prepare adsorbents for CO2 capture. The highest increment (200%) of CO2 capture capacity was observed for sono-aminated samples prepared at 600 and 700°C (maximum improvement for miscanthus), while biochars synthesized at 500 and 800°C demonstrated comparatively lesser increment in adsorption capacities that falls in the range of 115–151 and 127–159%, respectively compared to 600 and 700°C. The elevated pyrolysis temperature (particularly 600 and 700°C) resulted in increased %C and %ash contents and reduced %N contents with enhancement of micro surface area and pore volume. Thus, the superior adsorption capacity of miscanthus (at 600 and 700°C) can be attributed to their large surface areas (303–325 m2/g), high carbon contents (82–84%), and low ash contents (4–5%), as well as %N contents after sono-amination that was twice that of raw char

Urea functionalization of ultrasound-treated biochar: A feasible strategy for enhancing heavy metal adsorption capacity

© 2018 Elsevier B.V. The main objective of a series of our researches is to develop a novel acoustic-based method for activation of biochar. This study investigates the capability of biochar in adsorbing Ni(II) as a hazardous contaminant and aims at enhancing its adsorption capacity by the addition of extra nitrogen and most probably phosphorous and oxygen containing sites using an ultrasono-chemical modification mechanism. To reach this objective, biochar physically modified by low-frequency ultrasound waves (USB) was chemically treated by phosphoric acid (H3PO4) and then functionalized by urea (CO(NH2)2). Cavitation induced by ultrasound waves exfoliates and breaks apart the regular shape of graphitic oxide layers of biochar, cleans smooth surfaces, and increases the porosity and permeability of biochar\u27s carbonaceous structure. These phenomena synergistically combined with urea functionalization to attach the amine groups onto the biochar surface and remarkably increased the adsorption of Ni(II). It was found that the modified biochar could remove \u3e 99% of 100 mg Ni(II)/L in only six hours, while the raw biochar removed only 73.5% of Ni(II) in twelve hours. It should be noted that physical treatment of biochar with ultrasound energy, which can be applied at room temperature for a very short duration, followed by chemical functionalization is an economical and efficient method of biochar modification compared with traditional methods, which are usually applied in a very severe temperature (\u3e873 K) for a long duration. Such modified biochars can help protect human health from metal-ion corrosion of degrading piping in cities with aging infrastructure

Janus Reversal and Coulomb Blockade in Ferrocene-Perylenebisimide and <i>N</i>,<i>N</i>,<i>N</i>′,<i>N</i>′‑Tetramethyl-<i>para</i>-phenylenediamine-Perylenebisimide D‑σ‑A Rectifiers

Sandwiches “EGaIn|Ga₂O₃|LB monolayer of <b>2</b>|Au” and “EGaIn|Ga₂O₃|LB monolayer of <b>3</b>|Au” rectify. They are formed from a Langmuir–Blodgett (LB) monolayer of <b>2</b> or <b>3</b> transferred onto thermally evaporated gold. Molecules <b>2</b> and <b>3</b> are of the donor-sigma-acceptor (D-σ-A) type and have the same perylenebisimide (PBI) acceptor as previously studied molecule <b>1</b>. Molecule <b>1</b> has the weak donor pyrene, <b>2</b> has the good donor ferrocene, and <b>3</b> has the very strong donor <i>N</i>,<i>N</i>,<i>N</i>′<i>,N</i>′-tetramethyl-<i>p</i>-phenylenediamine (TMPD). All three molecules have a long swallowtail ending in a thioacetyl group, which ensures slow chemisorption onto the Au electrode. These molecules were contacted directly by a gallium indium eutectic (EGaIn) drop, covered by a defective oxide Ga₂O₃ layer. As before for <b>1</b>, the direction of rectification for <b>2</b> is bias-dependent. In the ±1.0 V range, the rectification is at positive V, with a rectification ratio (<i>RR</i>) that is initially greater than 5 and then decreases on successive scans to 2, while the currents decrease by as much as 2 orders of magnitude. In the ±2.5 V range, the rectification direction for <b>2</b> reverses, while upon repeated scanning the rectification ratio (in the negative direction) increases and the currents decrease. For molecule <b>3</b>, both directions have a charge-trapped state (Coulomb blockade) leading to <i>V</i>_offset in both biases, but at high potentials rectification set is, with large <i>RR</i> (up to 2,800) at ±2.5 V

Spectroscopy and rectification of three donor−sigma−acceptor compounds, consisting of a one-electron donor (pyrene or ferrocene), a one-electron acceptor (perylenebisimide), and a C19 swallowtail

We report spectroscopic characterization and unimolecular rectification (asymmetric electrical conduction) measurements of three donor-sigma-acceptor (D-sigma-A) compounds N-(10-nonadecyl)-N-(1-pyrenylmethyl)perylene-3,4,9,10-bis(dicarboximide) (1), N-(10-nonadecyl)-N-(4-[1-pyrenyl]butyl)perylene-3,4,9,10-bis(dicarboximide) (2), and N-(10-nonadecyl)-N-(2-ferrocenylethyl)perylene-3,4,9,10-bis(dicarboximide) (3). These molecules were arranged as one-molecule thick Langmuir-Blodgett monolayers between Au electrodes. In such an "Au | D-sigma-A | Au" sandwich, molecule 1 is a unimolecular rectifier, with rather small rectification ratios (between 2 and 3 at +/-1 V) that decrease upon cycling. Molecule 2 does not rectify. Molecule 3 rectifies, with a rectification ratio of between 14 and 28 at +/-1 V; the through-film rectification and currents persist, even with scans of +/-2 V, for up to 40 cycles of measurement. Qualitative arguments, based on a two-level rectification mechanism, are consistent with the current asymmetries observed in the monolayers of 1 and 3