There is an increasing interest to enhance resistance
to pathogens
on the powder-coated surface. Traditional silver antimicrobial agents
are hard to endure high curing temperature and lead to the yellowness
of the surface appearance. Commercial sources usually cut down silver
loading (less than 2.5 wt %) to avoid the color change and this will
result in a low inhibitory effect and poor durability. To improve
the antimicrobial performance and maintain the appearance, Ag+, Cu2+, and Zn2+ ternary inorganic antimicrobial
agents on Linde A zeolite supports were prepared in this study. The
silver content of this agent is increased to 8–10 wt % and
the coated surface exhibits high antimicrobial efficiency. The coating
appearance shows a little adverse color change (ΔE = 1.47) when adding 2 wt % amount of agent. The reduction rate of
this agent was over 99.99% after 6 h for Escherichia.
coli, Staphylococcus aureus, and Candida albicans according to
the ASTM E2180-07 standard, and the paint film can maintain over 99%
reduction rate even for 11 cleaning cycles. X-ray photoelectron spectroscopy
results show that Cu2+ is the main reduced ion during the
curing process, which protects Ag+ from reduction. The
leaching test confirms Zn2+ increases the number of extra
exchangeable cations, which can prolong the antimicrobial durability.
The selected molar ratio of Ag+, Cu2+, and Zn2+ is 1:2:3 according to quantitative study. Moreover, the
addition of fillers and pigments was slightly increased the color
change of the coated surface.
The triethylene glycol (TEG) was used to treat the off-gas stream containing 16 volatile organic compounds (VOCs) with high concentration (up to 15000 ppm) by experimental solvent absorption and ASPEN Plus computational simulation, respectively. This solvent absorption technology (SAT) not only purifies the off-gas but also recovers the VOCs. The effects of some typical operational parameters, including temperature, pressure, liquid loading rate, ratio of absorption liquid to gas flow rates, and absorption column height, on the absorption efficiency have been systematically investigated. Simulation results show that the optimal operational conditions are determined as 30 °C, 0.5 MPa (absolute), recycling TEG (with a purity of 99.9%) to a gas ratio of 4:1 by weight, and 8 theoretical stages. In addition, two stages of thermal coupling are applied minimizing the energy consumption of the off-gas absorption process, leading to a reduction of 89.77% in energy consumption. Laboratory experiments and field tests show that both VOCs absorption efficiency (using TEG as absorbent) and regeneration efficiency are highly consistent with those of ASPEN Plus simulation, suggesting the feasibility of simulation. Based on pilot-scale tests, the equipment investment and operational costs of SAT have been calculated and analyzed. Results show that the SAT is comparable with the traditional thermal treatment but with the advantages of much less secondary pollution. These findings indicate that the solvent absorption method is a promising green technology for treating high VOCs off-gas.
Nano-silver is characterized by broad-spectral, strong and stable antibacterial properties, which make it a promising material in coating applications. However, the efficiency of nano-silver is generally low in the coating of films. Here, we developed a series of highly active and durable silver ions–nano-silver antimicrobial agents for powder coatings. To optimize antimicrobial activity and durability, two different nano-silver generation methods, i.e., in situ and ex situ methods combined with different carrier materials, i.e., zeolite with high ion-exchange ability and montmorillonite of layered structure were adopted and investigated. All four antibacterial additives show high activity with a reduction rate of over 99.99% and R value of over 5. The ex situ generated nano-silver antibacterial agents with both carriers exhibit higher activity in the initial antibacterial property and antibacterial durability that the coating films are able to maintain over 99% antimicrobial reduction after 20 cycles (1200 times) of soap solution wiping. They also show a lower yellowish color difference of less than three compared to the films with in situ generation method. The one with montmorillonite as carrier shows the stronger antibacterial property with an R value of 5.88 and slightly better film appearance of lower color difference, smaller reduction in gloss and increase in haze as compared to zeolite carrier due to the layered structure.
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