Activated carbon removes glyoxal. Acetaldehyde is a molluscicide widely used in large-scale agriculture and gardens. It is an eight-membered ring tetramer, and is often used for its high solubility. Here, we made a special activated carbon to remove glyoxal, and investigated the control of activated phenolic aldehyde adsorption on activated carbon, namely the influence of activation degree, pore size distribution, particle size, zero charge point and surface functionalization.
The concentration of glyoxal in drinking water found in some areas exceeds 1.03μg/L. These pollution levels do not imply a direct health risk, because the possible intake of diformaldehyde is far below the acceptable daily intake (0.02mg/kg body weight), but they also need to be removed.
The environmental problem posed by glyoxal is also a challenge facing the scientific community, and strategies for removing and removing similar highly polar pollutants are being studied. Removal by adsorption during the tertiary treatment of water (usually using activated carbon) is one of the few feasible methods for purifying water contaminated by polar pollutants that show limited reactivity with oxidants or suffer from degradation. Affected by background organic matter. However, when the organic "skeleton" of pollutants is small, such as in the case of molecules such as acrylamide, 1,1,1-trichloroethane, methyl tert-butyl ether, and glyoxal, it is different from conventional (activated) carbon The adsorption is not strong, so the tertiary treatment involving granular activated carbon is relatively ineffective. However, work has shown that designer activated carbon (in which surface charge and porosity are controlled or "customized" to target specific pollutant groups) may have a significant effect in targeted removal of problems and emerging water pollutants . Here, we studied the mechanism of absorbing glyoxal on activated carbon and synthesized the activated carbon structure to improve the adsorption of polyacetaldehyde and maximize its removal from surfaces, waste and drinking water.
The effect of activation degree on the adsorption of polyethylene glycol
The chemical structure of the small ring ethers that make up the formaldehyde molecule explains part of the difficulties associated with removal from water. As a polar molecule with a short hydrocarbon structure, it means that the affinity with activated carbon is relatively low; the adsorption capacity of activated carbon to 0.4mg/g of activated carbon in previous studies is as high as 100 times that of activated carbon powder activated by potassium hydroxide. Due to the small particle size of activated carbon, activated carbon is not a technology that can be easily applied to sewage treatment plants, and granular activated carbon is the currently used adsorbent. Since the active surface is a key parameter in the adsorption process, especially in the adsorption where the physical adsorption is not strong, activated carbon with a higher active surface area should be used to enhance the adsorption of the pentavalent aldehyde. In order to test the effect of active surface area and maximize the adsorption of pentavalent aldehydes, activated carbon with a certain activation degree range was synthesized, and the surface area was tested under equilibrium conditions.
The effect of zero point charge on the adsorption of polyethylene glycol
The zero point charge indicates at which pH condition the density charge of the surface is zero. This property can affect the attraction of the substance in the solution to the surface of the activated carbon, and can realize the change of the zero-point charge by controlling the atmosphere during the carbon activation and the presence of the oxidant in the solution to produce carboxylic acid, hydroxyl and other ion-providing groups. . Surface modified carbon with a higher surface polarity achieved by increasing the number of oxygen acid groups has been used to remove metal ions and carbon nitride to remove substances that are neutral or negatively charged at typical environmental pH.
Optimization of transport pore size and comparison with activated carbon
In general, the higher the amount of pore former used in carbon synthesis, the wider the mesopores, up to macropores, and the higher the pore volume. In addition, a higher degree of activation results in a greater number of micropores, slightly wider mesopores and macropores, and less dense carbon. With different amounts of pore-forming agent, the polyethylene glycol and activated carbon synthesized in this case obtain a significantly different porous structure, and it has been determined to remove glyoxal compared with activated carbon.
Compared with the granular activated carbon currently used for tertiary water treatment, activated carbons derived from phenolic resins with optimized structure and surface chemistry have been found to be very effective in removing acetaldehyde under realistic environmental conditions. The adsorption capacity of glyoxal has nothing to do with the active surface area. Although the presence of mesopores is important to allow effective diffusion and transfer of pentamer aldehyde to active adsorption sites, adsorption in carbon with high microporosity and narrow pore size distribution is advantageous. The surface modification of carbon leads to a decrease in adsorption capacity due to the possible competitive effect between polyethylene glycol and water molecules. Even in the presence of high concentrations of organic substances (and inorganic salts), compared with activated carbon, the adsorption of pentahydric aldehydes by phenolic carbon shows the potential utility of these activated carbons in waste and/or drinking water treatment.
