Contributions of Various Cd(II) Adsorption Mechanisms by Phragmites australis-Activated Carbon Modified with Mannitol

Abstract

Due to its high toxicity, persistence, and bioaccumulation in the food chain, controlling cadmium (Cd) pollution in wastewater is urgent. Activated carbon is a popular material for removing Cd. To improve the Cd(II) adsorption efficiency by increasing the number of oxygen-containing functional groups, Phragmites australis -activated carbon (PAAC) was modified with mannitol at a low temperature (150 °C). The textural and chemical characteristics of PAAC and modified PAAC (M-PAAC) were analyzed by surface area analysis, elemental analysis, Boehm’s titration, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy. Batch adsorption experiments were conducted to investigate the influence of Cd(II) concentration, contact time, ionic strength, and pH on Cd(II) adsorption. The main adsorption mechanisms of Cd(II) on activated carbon were quantitatively calculated. The results showed that mannitol modification slightly decreased the S BET (5.30% of PAAC) and increased the content of carboxyl, lactone, and phenolic groups (total increase of 43.96% with PAAC), which enhanced the adsorption capacity of PAAC by 58.59%. The adsorption isotherms of PAAC and M-PAAC were described well using the Temkin model, while the intraparticle diffusion model fitted the Cd(II) adsorption kinetics best. Precipitation with minerals was a crucial factor for Cd(II) adsorption on activated carbon (50.40% for PAAC and 40.41% for M-PAAC). Meanwhile, the Cd(II) adsorption by M-PAAC was also dominated by complexation with oxygen-containing functional groups (33.60%). This research provides a method for recovering wetland plant biomass to prepare activated carbon and efficiently treat Cd-containing wastewater.

Preparation of Tetra Pak-Based Hydrochars for Cleaning Water Polluted by Heavy Metal Ions: Physicochemical Properties and Removal Mechanism

“…Tese changes suggest that Zn 2+ and Pb 2+ ions bind to the hydroxyl and carbonyl groups of cellulose and the carbon phase contained in hydrochars [51][52][53][54]. Similar results have been reported by Zhan et al [55], Xia et al [56], and Jiang et al [57] for the Cu 2+ , Zn 2+ , and Pb 2+ adsorption on lignocellulosic adsorbents, hydrochars, and activated carbons. On the other hand, the characterization analysis of hydrochar used in Hg 2+ adsorption suggested the participation of carbonyl groups and aluminum-silicon moieties in the removal mechanism, as the absorption bands located below ∼1700 cm −1 underwent a considerable decrease in their intensity [58,59].…”

Efficient Removal of Nickel from Wastewater Using Copper Sulfate–Ammonia Complex Modified Activated Carbon: Adsorption Performance and Mechanism

“…Considering the crucial role of functional groups in heavy metal adsorption [36], FTIR spectral analysis and a Boehm titration experiment were employed to identify and quantify the functional groups on PAC and [Cu(NH 3 ) 4 ]-PAC surfaces (Figure 1b,c). The wide peak band observed between 3397 cm −1 and 3436 cm −1 was assigned to the -NH 2 or -OH functional groups associated with phenols, alcohols, and carboxylic acids [36,37]. Additionally, the peaks at 672 cm −1 and 2922 cm −1 were indicative of alkene C-H stretching vibrations and the C-H bonds in lignin, hemicellulose, and cellulose, respectively [37,38].…”

“…The wide peak band observed between 3397 cm −1 and 3436 cm −1 was assigned to the -NH 2 or -OH functional groups associated with phenols, alcohols, and carboxylic acids [36,37]. Additionally, the peaks at 672 cm −1 and 2922 cm −1 were indicative of alkene C-H stretching vibrations and the C-H bonds in lignin, hemicellulose, and cellulose, respectively [37,38]. The peak of aromatic C=C, ketone, or carbonyl C=O appeared near 1559 cm −1 [39].…”

“…The total acidic functional groups in [Cu(NH 3 ) 4 ]-PAC, encompassing carboxyl, lactone, and phenolic groups, amounted to 2.403 mmol/g, exceeding that of PAC (2.033 mmol/g). An elevated concentration of acid groups is advantageous for the removal of heavy metal ions from aqueous solution [37]. Post-modification, the quantity of alkaline groups increased from 1.332 mmol/g to 1.639 mmol/g.…”

Functional biochar as sustainable precursors to boost the anaerobic digestion of waste activated sludge from a circular economy perspective: a review

“…In recent years, several innovative technologies and green materials have been employed in organic modification to reduce costs, minimize toxicity, and mitigate environmental pollution. For instance, using bioactive substances extracted from plants (Jiang et al 2022a) and microorganisms as modifiers can significantly reduce costs and environmental impact.…”