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A Y-type zeolite was prepared from illite clay, which was activated and synthesized by a solid-phase alkali fusion technique with reduced reaction conditions and crystal methods. The optimal synthesis conditions were investigated using the Box-Behnken design for a NaOH/illite (mass ratio) of 1:2, an activation temperature of 185 °C, and an activation time of 2.7 h. The synthesized Y-type zeolites were characterized by various analytical techniques such as FT-IR, XRD, and SEM, and the results obtained show that small amounts of quartz and P-type zeolites are present in the synthesized products. The mixture was classified as a zeolitic mineral admixture (ZMA). The adsorption performance of ZMA on Pb(II) and Cu(II) in solution was evaluated by batch adsorption experiments. The results showed that ZMA had good adsorption performance for Pb(II) and Cu(II), with maximum adsorption amounts of 372.16 and 53.46 mg/g, respectively. From the investigation, it was concluded that the adsorption process is chemisorption occurring in monomolecular layers and relying on electrostatic adsorption, ion exchange and complexation of hydroxyl groups on the ZMA surface for heavy metal cations. The ZMA reusability result shows that sodium chloride has the ability to regenerate the active site by restoring the ion exchange capacity without significant loss of Pb(II) and Cu(II) adsorption. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Chitosan-based flocculants with chelation and flocculation capacity are designed and prepared. • Relationship between flocculants structural and chelation-flocculation is investigated. • There is a certain linear relationship between heavy metal concentration and flocculants dosage. • Copper ions in mixed heavy metals solutions is preferentially chelated and flocculated. • The work provided valuable guidance in the design of eco-friendly polymeric flocculants. Abstract Dual-function chitosan-based flocculants with chelation and flocculation capacity, carboxylated chitosan-graft-polyacrylamide (PCA), carboxylated chitosan-graft-polyacrylamide-co-sodium xanthate (PCAXC), and carboxylated chitosan-graft-poly(acrylamide-2-acrylamido-2-methylpropane sulfonic acid) (PCAAF), are designed and prepared by UV initiation method. The physicochemical characteristics of PCA, PCAXC, and PCAAF were characterized by fourier transform infrared spectroscopy, 1H nuclear magnetic resonance, and X-ray diffraction pattern to confirm the successful syntheses. Then PCA, PCAXC, and PCAAF are applied to chelate and flocculate Cu, Cr, and Ni from water. Effects of pH, flocculants dosage, reaction time, and stirring speed were investigated systematically to detect the relationship between flocculants structural and chelation-flocculation capacity. The maximum removal rate of Cu and Cr obtained by PCAXC at are 85.1% and 76.1%, respectively, while The maximum removal rate of Ni obtained by PCAAF at is more than 75.7%%. In addition, the relationship between the initial concentration of simulated heavy metal wastewater and the flocculants dosage and the competitive chelation-flocculation properties in the mixed heavy metal solution are also detected in detail. The mechanism can be assigned to the effective interaction between function groups of the flocculants and heavy metal irons by chelation, charge neutralization, and adsorption bridging mechanism. [ABSTRACT FROM AUTHOR]

In this work, carboxylated chitosan and acrylamide are used to synthesize a graft-modified natural polymer flocculant carboxylated chitosan-graft-acrylamide (CCSPAM) by UV-induced polymerization for copper and chromium removal. The effects of total monomer concentration, monomer mass ratio, pH value, photoinitiator concentration, and illumination time on the synthesis performance of CCSPAM were investigated regarding intrinsic viscosity (IV), grafting rate (GR), and grafting efficiency (GE). Various analytical techniques characterize the physicochemical characteristics of CCSPAM. Single factor experiments are used to investigate the effect of dosage, pH value, and reaction time on the chelation and capture of heavy metal ions by CCSPAM. The results show that the optimal IV, GR, and GE of CCSPAM achieved at total monomer concentration 30%, monomer mass ratio 1:4, pH 7.0, photoinitiator concentration 0.03%, and irradiation time 2 h are 1412.2 mL/g, 394.1%, and 84.1%, respectively. The experimental data of flocculation show that CCSPAM has a good total Cu and total Cr removal efficiency of 74.8% and 70.6% at dosage 2.0 mg/L, pH 6.0, and reaction time 2h, respectively. Fom the investigation, it is concluded that the grafted chitosan (CCSPAM) could be a be an effective and eco-friendly flocculant for removal of total Cu and total Cr ions from aqueous system. [ABSTRACT FROM AUTHOR]

In this study, a high-efficiency magnetic heavy metal flocculant MF@AA was prepared based on carboxymethyl chitosan and magnetic Fe3O4. It was characterized by SEM, FTIR, XPS, XRD and VSM, and the Cu(II) removal rate was used as the evaluation basis for the preparation process. The effects of AMPS content, total monomer concentration, photoinitiator concentration and reaction time on the performance of MF@AA flocculation to remove Cu(II) were studied. The characterization results show that MF@AA has been successfully prepared and exhibits good magnetic induction characteristics. The synthesis results show that under the conditions of 10% AMPS content, 35% total monomer concentration, 0.04% photoinitiator concentration, and 1.5 h reaction time, the best yield of MF@AA is 77.69%. The best removal rate is 87.65%. In addition, the response surface optimization of the synthesis process of MF@AA was performed. The optimal synthesis ratio was finally determined as iron content 6.5%, CMFS: 29.5%, AM: 53.9%, AMPS: 10.1%. High-efficiency magnetic heavy metal flocculant MF@AA shows excellent flocculation performance in removing Cu(II). This research provides guidance and ideas for the development of efficient and low-cost flocculation technology to remove Cu(II) in wastewater. [ABSTRACT FROM AUTHOR]

This field study aims to identify the performance and mechanisms of red soil amelioration and heavy metal immobilization by a multi-element mineral amendment (MMA) mainly containing a mixture of zeolites (laumontite and gismondine), montmorillonite, gehlenite, grossular and calcium silicate powder. The results indicated that the acidity of red soil was neutralized, and the soil EC, CEC, and content of montmorillonite and illite were increased after application of MMA, improving the soil fertility as well as the ability of heavy metals immobilization. The high amounts and reactivity of dissolved and colloidal Fe provided by the ferralsol (red soil) combined with the abundant available Si, Ca, Mg, Na and K supplied by MMA, readily destabilizes kaolinite and facilitates the formation of 2:1 type clay minerals. Meanwhile, the application of MMA was effective in reducing the bioavailability of soil heavy metals due to the activated mineralogical compositions of MMA as well as the increase of pH and 2:1 type clay minerals in the soil, which significantly decreased the up-taking and accumulation of Cd, Pb, Cr and Hg in lettuce tissues (p < 0.05). Compared with the untreated soil, the plant height, the total yield and content of vitamin C in the edible parts of lettuce in MMA-treated soil was increased by 7.6%, 23.6%, and 12.8%, respectively. These results showed that MMA could be a promising amendment for red soil amelioration and heavy metal immobilization. Image 1 • 1:1 type clay mineral in red soil transformed into 2:1 type clay mineral after application of MMA. • MMA was effective in reducing the bioavailability of heavy metals in red soil. • Application of MMA significantly improved the yield and quality of lettuce. [ABSTRACT FROM AUTHOR]

Herein, graphene oxide (GO) was successfully functionalized on the multifunctional β−cyclodextrin chitosan polymer through EDTA crosslinking (GO@CS−EDTA−β−CD) for the adsorption of toxic inorganic and organic micropollutants from water. This unique adsorbent possesses important adsorptive features from each component: chitosan works as a backbone of the polymer chain, β−CD cavities adsorb the organic micropollutants via the host-guest inclusion complexation, EDTA acts as a crosslinker and provides complexation sites for heavy metal ions and GO can interact with both organic and inorganic micropollutants. After complete characterization, the polymer were explored on the adsorption of inorganic micropollutants (i.e., Hg(II), Pb(II), Cu(II) and Ni(II)) and organic one (i.e., methylene blue, MB) under different experimental conditions. In monocomponent systems, the adsorption followed the pseudo-second order (PSO) kinetics for both heavy metals and MB dye. The adsorption isotherms of heavy metals and MB followed the Langmuir and Sips models, respectively. The maximum adsorption capacities were found to be 364.90 ± 15.20, 287.40 ± 10.0, 130.40 ± 6.50, 98.90 ± 3.10, 158.40 ± 5.10 mg g−1 for Hg(II), Pb(II), Cu(II), Ni(II) and MB, respectively. In binary component systems, dye adsorption was not affected by metal ions, while the adsorption efficiency for metal ions was increased by the MB presence: possibly due to synergism. Additionally, the prepared adsorbent showed good efficiency without any significant loss in adsorption capacity even after six continuous regeneration cycles, confirming its superior reusability and stability. In short, excellent removal efficiencies for the metal ions and MB at environmental levels in model textile effluent, synthetic acid mine water make the adsorbent promising in treating water contaminated by heavy metals and/or dyes. [Display omitted] • Investigated effect of GO on adsorption selectivity of CS−EDTA−β−CD. • Obtained adsorption capacities of 364.90–98.90 ± 3.10 mg g−1 for heavy metals and MB. • Observed synergetic effect on adsorption of metal ions in Cu2+−MB binary system. • Confirmed adsorption mechanisms by elemental mapping, EDS and FTIR analysis. • Obtained removal efficiency of 85.2% and 85.0% for Cu and MB even after sixth cycle of adsorption. [ABSTRACT FROM AUTHOR]

[Display omitted] • A high-efficiency, multifunctional, salt/pH-tolerant magnetic flocculant was successfully prepared. • The growth characteristics of flocs are systematically elucidated. • There is a positive correlation between the fractal dimension of flocs and flocculation efficiency. • Ca(II) and Fe(III) will promote the removal of DB56 and Cu(II), respectively. • The neural network models can accurately predict the removal rate of DB56 and Cu(II). In this study, an amphoteric magnetic chitosan (CS)-based flocculant MFe 3 O 4 @CS-g-PIA was prepared from CS, Fe 3 O 4 , and itaconic acid (IA), and its apparent morphology and characteristic structure were systematically studied. The flocculation performance and mechanism of the fabricated material were also investigated in different pollution systems, and the effects of total monomer concentration, m(CS):m(IA), IA pre-neutralization degree, reaction temperature, reaction time, and initiator concentration on the synthesis of MFe 3 O 4 @CS-g-PIA were studied. Characterization results showed that MFe 3 O 4 @CS-g-PIA forms a three-dimensional network with excellent magnetic induction. The optimal removal rates of Cu(II) and Disperse Blue 56 (DB56; 90.2% and 97.0%, respectively) were obtained under the conditions of 150 mg·L−1 MFe 3 O 4 @CS-g-PIA, pH 6.0, and 300 rpm stirring speed. MFe 3 O 4 @CS-g-PIA maintained removal rates of over 80.0% for Cu(II) and DB56 after five consecutive cycles of regeneration/flocculation and demonstrated excellent acid resistance stability. Changes in the particle size distribution, fractal dimensions, and zeta potentials of the flocs indicated that the relevant flocculation mechanism involves the synergistic functions of chelation, charge neutralization, and adsorption bridging. An artificial neural network model was finally established on the basis of the experimental flocculation data to predict the removal rates of Cu(II) (R = 0.97) and DB56 (R = 0.98) accurately. [ABSTRACT FROM AUTHOR]