Search

A cellulose-based bio-absorbent with various and plenty of amino groups was successfully prepared from corn stalk to achieve quantitative removal of Congo red from wastewater with wide pH values (5 ≤ pH ≤ 10). The maximum removal amount was 8.0 mmol·g−1 (5572 mg·g−1) under pH = 6.0 and 45 °C, which was obviously higher than reported absorbents. Investigation on dynamic adsorption and recyclability in authentic wastewater found that the removal efficiency of Congo red was >98 % within 180 min and decreased slightly in industrial water after five cycles, denoting this adsorbent with great potential for environmental application. The characterization results proved that 7.58 mmol·g−1 of different amino groups (-NH 2 , -NH- and -NR 2) were introduced on adsorbent surface by two steps of modification and were the major functional groups for adsorption of Congo red. The inferred adsorption mechanism revealed that Congo red could be adsorbed equivalently on the amino groups by strong electrostatic interactions or hydrogen bonds. Different amino groups played different roles in adsorption due to great differences in protonation ability in 5 ≤ pH ≤ 10. The study was expected to high-efficiently remove Congo red from acidic or alkaline wastewater, and offered an alternative strategy for biowaste treatment of corn stalks in a high value-added manner. [Display omitted] [ABSTRACT FROM AUTHOR]

A composite (ZS–UiO–66–NH 2) zirconium crosslinked sodium alginate gel beads (ZS)–metal–organic skeleton (UiO–66–NH 2) were prepared in this study through in–situ growth under simple, green and mild conditions for removal of the salicylic acid (SA) and sulfosalicylic acid (SSA) from water. The physicochemical properties of ZS–UiO–66–NH 2 were characterized using various analytical methods. The influencing factors in the adsorption process including pH of solution, amount of adsorbent, coexisting ions, adsorption time, reaction temperature and equilibrium concentration of SA/SSA were performed in batch adsorption. The experimental results indicated that ZS–UiO–66–NH 2 had high stability and could achieve efficient adsorption of SA/SSA in broad pH range (2–9) and salinity (0–0.2 mol·L−1). SA and SSA adsorbed on the composite at 293 K reached high values of 193 and 167 mg·g−1 from Langmuir model, respectively. Kinetic and isotherm studies demonstrated that the adsorption processes were mainly multilayer heterogeneous chemisorption. Thermodynamic data manifested that the two processes were exothermic and spontaneous with increasing entropy. ZS–UiO–66–NH 2 can effectively remove SA/SSA from simulated wastewater under different pH and can be reused after elution with a NaHCO 3 solution (5 mmol·L−1). The ZS–UiO–66–NH 2 composite has great potential for removing SA/SSA from actual water bodies. • The preparation process of ZS–UiO–66–NH 2 is simple, green and economical. • ZS–UiO–66–NH 2 has high adsorption performance for SA and SSA. • The two adsorption processes of SA and SSA show wide pH application range. • ZS–UiO–66–NH 2 has ideal recycling performance. [ABSTRACT FROM AUTHOR]

In this work, the modified‑sodium alginate gel beads were prepared by sol-gel method. Due to the presence of water channels in the sodium alginate gel bead, amidoxime groups and PO 4 3− were exposed to the surface of the adsorbent to the maximum extent, resulting in the excellent adsorption capacity of modified‑sodium alginate gel beads. The introduction of amidoxime-modified hydroxyapatite significantly improved the adsorption capacity and the adsorption rate of the gel beads. The adsorption capacity increased from 308.7 to 466.0 mg/g and the adsorption equilibrium time was shortened from 300 min to 120 min. The modified‑sodium alginate gel bead possessed the advantages of short adsorption time, high adsorption efficiency and large adsorption capacity, which could be regarded as a potential adsorbent for uranium. Moreover, the uranium removal ability on the modified gel beads was mainly attributed to the Coulomb force between PO 4 3− and uranium and the complexation between uranium and amidoxime groups. In summary, this work would provide a new idea for the modification and application of sodium alginate-based materials. [Display omitted] • A new sodium alginate-based gel bead was effectively created. • AO@HAP&SA was used for uranium removal with high adsorption affinity. • The saturated adsorption capacity of AO@HAP&SA reached 466.0 mg/g. • The introduction of AO groups broadened the pH usage range of SA. [ABSTRACT FROM AUTHOR]

In this work, the modified‑sodium alginate gel beads were prepared by sol-gel method. Due to the presence of water channels in the sodium alginate gel bead, amidoxime groups and PO 4 3− were exposed to the surface of the adsorbent to the maximum extent, resulting in the excellent adsorption capacity of modified‑sodium alginate gel beads. The introduction of amidoxime-modified hydroxyapatite significantly improved the adsorption capacity and the adsorption rate of the gel beads. The adsorption capacity increased from 308.7 to 466.0 mg/g and the adsorption equilibrium time was shortened from 300 min to 120 min. The modified‑sodium alginate gel bead possessed the advantages of short adsorption time, high adsorption efficiency and large adsorption capacity, which could be regarded as a potential adsorbent for uranium. Moreover, the uranium removal ability on the modified gel beads was mainly attributed to the Coulomb force between PO 4 3− and uranium and the complexation between uranium and amidoxime groups. In summary, this work would provide a new idea for the modification and application of sodium alginate-based materials. [Display omitted] • A new sodium alginate-based gel bead was effectively created. • AO@HAP&SA was used for uranium removal with high adsorption affinity. • The saturated adsorption capacity of AO@HAP&SA reached 466.0 mg/g. • The introduction of AO groups broadened the pH usage range of SA. [ABSTRACT FROM AUTHOR]