Coconut Shell Activated Carbon Supported Quaternary Ammonium for Continuous Cycloaddition of CO₂ and Biogas Upgrading in a Packed Bed

Quaternary ammonium was successfully prepared on coconut shell activated carbon (CSAC) granules. The samples were characterized by FT-IR, N₂ adsorption–desorption, XPS, TG, and EA. The immobilized quaternary ammonium was thermally stable below 320 °C. The amount of immobilized quaternary ammonium on the CSAC was 0.957 mmol/g. Continuous cycloaddition of CO₂ to epichlorohydrin (ECH) was carried out in a packed-bed reactor without using solvent or cocatalyst. When the reaction conditions were 130 °C and 1.4 MPa, the conversion of ECH and the corresponding turnover frequency (TOF) were 43.5% and 64.6 h^–1, respectively. The selectivity to epichlorohydrin carbonate (ECHC) reached ∼100%. In biogas upgrading, grafting of quaternary ammonium was demonstrated to enhance CO₂ capture capacity of the CSAC. The saturated CO₂ capture capacities of the CSAC and the quaternary ammonium functionalized CSAC were 1.82 and 2.40 mmol/g at 20 °C and 0.5 MPa, respectively. The adsorption selectivities of CO₂ over CH₄ were ∼67% and 85% for the CSAC and the supported quaternary ammonium, respectively. The adsorption heat was 20–30 kJ/mol for the adsorbents. The supported quaternary ammonium also exhibited a relatively stable cyclability in a packed bed

Development of Coconut Shell Activated Carbon-Tethered Urease for Degradation of Urea in a Packed Bed

Coconut shell activated carbon (AC)-tethered urease (from jack bean) was successfully developed to degrade urea in a packed bed reactor. The loading capacity of urease in AC was 78.8 mg/g. The tethered enzyme showed a maximum activity at 70 °C and pH 7.2. For higher than 75% of the maximum activity, the tethered urease showed a broader temperature range of 42–80 °C compared to 45–75 °C for the free enzyme. Similarly, the tethered urease had an increased stability against the changes of pH. The <i>K</i>_m value of the free urease was 0.271 mol/L and 0.345 mol/L for the tethered one. This may be caused by the conformational changes of the enzyme. The <i>V</i>_max values were 0.215 and 0.110 mol/min for the tethered and free ureases, respectively, which is reflected by an increase in catalytic activity. The catalytic degradation of urea was performed in a packed bed reactor. The remaining activity of the tethered urease was over 80% after 50 h of operation

Acute toxicity-associated pathological changes in Wistar rats manifested as atelectasis.

<p>A) The group receiving deltamethrin degradation mixture; B) The control group receiving residual deltamethrin.</p

Delayed toxicity-associated pathological changes occurred mainly in the spleen, including fibrosis and lymphoid tissue hyperplasia.

<p>A) The group receiving deltamethrin degradation mixture; B) The control group receiving residual deltamethrin.</p

One of the main deltamethrin degradation products with the molecular formula of C₁₃H₁₀O₂.

<p>One of the main deltamethrin degradation products with the molecular formula of C₁₃H₁₀O₂.</p

The survival and death of Wistar rats after treatment of deltamethrin or its degradation products.

<p>√ survival, × death.</p

Percentage of deltamethrin degraded in trypsin-catalyzed reactions.

<p>Percentage of deltamethrin degraded in trypsin-catalyzed reactions.</p

<i>Culex pipiens pallens</i> mosquito mortality rate in standard WHO deltamethrin resistance bioassay.

<p><i>Culex pipiens pallens</i> mosquito mortality rate in standard WHO deltamethrin resistance bioassay.</p

Values of 50% lethal concentration (LC₅₀) in Tangkou population of <i>Culex pipiens pallens</i> in response to deltamethrin selection.

<p>*Resistance ratio is the ratio of LC₅₀ of the test population to LC₅₀ of the initial parental (G₀) population.</p

Dynamics of <i>kdr</i> allele frequency in response to deltamethrin selection.

<p><b>A</b>: wildtype L1014 allele frequency was significantly decreased under deltamethrin selection, but significantly increased in the absence of selection; <b>B</b>: L1014F allele frequency was significantly increased under selection, but significantly decreased when no insecticide selection pressure was available; and <b>C</b>: L1014S allele frequency was decreased regardless of deltamethrin selection.</p