To cope with the widespread polyfluoroalkyl substance
(PFAS) pollution
in the global aquatic environment, this study prepared an acid-modified
biochar adsorbent derived from sludge with satisfactory performance.
The theoretical maximum adsorption capacities of the adsorbent for
perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA)
were determined to be 72.17 and 45.88 mg·g–1, respectively. The theoretical calculation of the adsorption of
biochar surface functional groups with PFOS and PFOA was first performed
in this study, and the mechanism of the adsorption process was inferred
with a combination of experimental results and redundancy analysis.
The adsorption mechanism is composed mainly of the following three
aspects: (I) electrostatic interaction between the positively charged
biochar and the deprotonated PFAS; (II) hydrogen bonding between anionic
species of PFAS and functional groups; and (III) hydrophobic interaction
between long-chain hydrophobic PFAS and biochar. Electrostatic interaction
plays a major role in the three main adsorption mechanisms under acidic
media. Meanwhile, different functional groups have different adsorption
energies for PFAS, and CO has the highest adsorption energy.
The findings in this work could provide great insights into the adsorption
of PFAS on modified biochar as an environmentally friendly adsorbent
to promote resource reuse, improve water quality, and ensure human
health.
Freshwater production is critical in terms of solving the global water shortage. Aiming at improving freshwater production capability and ensuring its quality, an interfacial charge-modulated MoS 2 /Ti 3 C 2 T x -modified carbon fiber (CF/ MoS 2 /Ti 3 C 2 T x ) penetrating electrode is designed. To maximize the desalination and degradation efficiencies of CF/MoS 2 /Ti 3 C 2 T x , a photocatalytic component is introduced into the membrane capacitive deionization (PMCDI) device. High desalination capability is derived from the lamellar architecture structure of MoS 2 /Ti 3 C 2 T x . Meanwhile, excellent degradation performance is due to the formation of two photoelctrocatalytic activity centers, directionally generating singlet oxygen ( 1 O 2 ) and hydroxyl radical ( • OH). The intercalated Cl − (desalination) as the electron transfer bridge optimizes the charge distribution of MoS 2 /Ti 3 C 2 T x , reinforcing the photoelectrocatalytic activity (degradation). The formation of the electron-deficient (desalination) and electron-rich (regeneration) regions at the terminated O atom of Ti 3 C 2 T x accelerate the generations of • OH and 1 O 2 , respectively. In perspective, a mutual promotion process of desalination and degradation is achieved for high-efficiency production of high-quality freshwater. KEYWORDS: penetrating electrode, Ti 3 C 2 T x MXene, MoS 2 , membrane capacitive deionization, freshwater production
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