Adsorptive properties of sulfolignin–polyacrylamide graft copolymer for lead and uranium: Effect of hydroxilamine–hydrochloride treatment

Hierarchical build-up of vertically oriented lignin-based aerogel for photothermally assisted uranium uptake and recovery from acidic wastewater

Developing the lignin-based functional materials for uranium uptake is extremely attractive, but challenging due to the complex structure, poor solubility and reactivity of lignin. Herein, a novel phosphorylated lignin (LP)/sodium alginate/ carboxylated carbon nanotube (CCNT) composite aerogel (LP@AC) with vertically oriented lamellar configuration was created for efficient uranium uptake from acidic wastewater. The successful phosphorylation of lignin by a facile solvent-free mechanochemical method achieved more than six-times enhancement in U(VI) uptake capacity of lignin. While, the incorporation of CCNT not only increased the specific surface area of LP@AC, but also improved its mechanical strength as a reinforcing phase. More importantly, the synergies between LP and CCNT components endowed LP@AC with an excellent photothermal performance, resulting in a local heat environment on LP@AC and further boosting the U(VI) uptake. Consequently, the light irradiated LP@AC exhibited an ultrahigh U(VI) uptake capacity (1308.87 mg g^-1), 61.26% higher than that under dark condition, excellent adsorptive selectivity and reusability. After exposure to 10 L of simulated wastewater, above 98.21% of U(VI) ions could be rapidly captured by LP@AC under light irradiation, revealing the tremendous feasibility in industrial application. The electrostatic attraction and coordination interaction were considered as the main mechanism for U(VI) uptake.

Simultaneous removal of methylene blue and Pb2+ from aqueous solution by adsorption on facile modified lignosulfonate

In this paper, simultaneous removal of methylene blue (MB) and Pb²⁺ from the binary component system by an easily prepared cross-linked lignosulfonate bio-adsorbent (CLLS) was described. CLLS was characterized by FTIR, SEM/EDS and TGA. The influences of pH, temperature, contact time and initial MB and Pb²⁺ concentrations on the adsorption performance were investigated. The results demonstrated a good ability of CLLS to remove MB and Pb²⁺ simultaneously. Using of 1.0 g L^-1 loading, removal efficiency of MB and Pb²⁺ reached 98.0% and 97.8%, respectively, in the MB (100 mg.L^-1)-Pb²⁺ (50 mg.L^-1) system. Moreover, the adsorption isotherms and adsorption kinetics indicated that the results were fitting well with the Langmuir and pseudo-second-order model, respectively, for both MB and Pb²⁺. Based on the Langmuir model, the maximum adsorption capacity of MB and Pb²⁺ reached 132.6 and 64.9 mg g^-1, respectively, in the MB-Pb²⁺ system, which was much lower than that in the single component system (358.4 mg g^-1 100.9 mg g^-1 for MB and Pb²⁺, respectively). Hence, simultaneous adsorption of MB and Pb²⁺ onto CLLS was an antagonistic adsorption. In addition, an apart-sequential adsorption method was used to study the action of adsorption sites on CLLS for MB and/or Pb²⁺ with the help of an efficient self-made apparatus. Rudimental results showed that there would be three different kinds of adsorption sites on CLLS: MB-site, Pb²⁺-site and MB/Pb²⁺- shared sites. Furthermore, in the MB (100 mg.L^-1)-Pb²⁺(50.0 mg.L^-1) system, the simultaneous removal efficiency of MB and Pb²⁺ still maintained 91.8% and 85.0%, respectively, after 6 cycles.

Synthesis and characterization of a composite polymeric material including chelating agent for adsorption of uranyl ions

In this study, a versatile polymeric material was synthesized by grafting Calcon Carboxylic Acid (CCA), which is known as a chelating agent for some metal ions, to polyacrylamide (PAA) structure. Thus, the adsorptive properties of inert PAA polymer were significantly improved owing to this procedure. The obtained new material, CCA-g-PAA, was characterized by point zero charge (PZC), FTIR, SEM, and UV-VIS-NIR analysis. The adsorption properties of new material were investigated comprehensively and experimental variables were optimized such as pH, temperature, time, and concentration. Experimental data were evaluated by using theoretical adsorption models. The maximum adsorption capacity of material was calculated as 0.079molkg^-1 by considering Langmuir equation. The constants calculated from Freundlich and DR model were found as 6.98 and 0.441, respectively. Adsorption kinetic was also explained with pseudo second order and intra particular diffusion models. Experimental studies were showed that adsorption was endothermic and occurred spontaneously. The developed material has important advantages such as reusability, cost-effective synthesis procedure, high adsorption capacity, and selectivity.

Preparation of acrylonitrile/acrylamide copolymer beads via a redox method and their adsorption properties after chemical modification

Poly(acrylonitrile-co-acrylamide) [poly(AN-co- AM)] was prepared via a redox method, with sodium bisulfite and potassium persulphate as the initiators. High yield was attained in up to 76% of monomer conversion within 3 h of reaction time. The copolymers were then chemically modified with hydroxylamine hydrochloride to obtain amidoxime functional groups in the polyacrylonitrile (PAN) system. The role of the amidoxime group is to form a chelating ion-exchange network based on acrylonitrile for the adsorption of heavy metal ions in aqueous solution. Based on the Fourier transform infrared spectra, the appearance of a strong band at the regions of 1680 and 3300–3400 cm-1 due to the stretching vibration of C=O and NH2 groups, respectively, confirmed the copolymerization of acrylamide into the PAN system. In the case of modified copolymers, there was an appearance of broad bands at the regions of ∼3300 and ∼900 cm-1, which corresponded to the stretching vibrations of O-H and =N-O, respectively, from the oxime group. The scanning electron microscopy showed that the average size of the copolymer particles was ∼149 nm, and the average size increased to ∼217 nm in the case of the modified copolymer. The amidoximed poly(AN-co-AM) was analyzed by inductively coupled plasma to investigate its adsorption behavior toward Cu(II).

Removal of uranyl ions in aquatic mediums by using a new material: gallocyanine grafted hydrogel

A new material containing gallocyanine (GC) grafted polyacyril amide (PAA) was synthesized and its adsorption ability was examined for the removal of uranyl ions from aqueous media. The new developed adsorbent was characterized by FTIR, SEM, and PZC analysis. Adsorption of UO₂(2+) ions from aqueous solution as a function of ion concentration, pH, ionic strength, temperature, and reusability of adsorbent was investigated in detail. The adsorption data were analyzed by using the Langmuir, Freundlich and Dubinin-Radushkevich (DR) models. The adsorption of UO₂(2+) increased with pH and reached a plateau value in the pH range 5-6. The adsorption of UO₂(2+) ions were not affected by increasing ionic strength. The adsorption mechanism followed an endothermic and spontaneous process with increased disorderliness at adsorbate/adsorbent interface. The adsorption process followed a pseudo-second-order kinetics. The new developed material is a potential adsorbent for effective removal of uranyl ions from aquatic solutions.