Lignin extraction from barley straw using ultrasound-assisted treatment method for a lignin-based biocomposite preparation with remarkable adsorption capacity for heavy metal

Capturing effects of filamentous fungi Aspergillus flavus ZJ-1 on microalgae Chlorella vulgaris WZ-1 and the application of their co-integrated fungi-algae pellets for Cu(II) adsorption

Using filamentous fungi to capture unicellular microalgae is an effective way for microalgae recovery in water treatment. Here, fungi Aspergillus flavus ZJ-1 and microalgae Chlorella vulgaris WZ-1 isolated from a copper tailings pond were used to study the capture effect of ZJ-1 on WZ-1. The highest capture efficiency (97.85%) was obtained within 6 h under the optimized conditions of 30 °C, 150 rpm, fungi-algae biomass ratio of 2.24:1, and initial pH of 9.24 in microalgae medium. The formed fungi-algae pellets (FAPs) were further used to remove Cu(II) from aqueous solution. Results showed that the FAPs formed at different capture times all adsorbed Cu(II) well, and the PAFs formed within 2 h (PAFs_2 h) exhibited the highest Cu(II) adsorption capacity (80.42 mg·g^-1). SEM images showed that Cu(II) caused a change in the internal structure of PAFs_2 h from loose to compact, the mycelium shrunk, and the microalgal cells were concave. Cu(II) adsorption by PAFs_2 h was well conformed to the pseudo-second-order kinetics and the Langmuir isotherm (123.61 mg·g^-1 of theoretically maximum adsorption capacity). This work opens a way for applying FAPs in the remediation of heavy metal-contaminated wastewater, and the metal adsorption effect was determined by the capture amount of microalgae.

Study on Preparation of Chitosan/Polyvinyl Alcohol Aerogel with Graphene-Intercalated Attapulgite(GO-ATP@CS-PVA) and Adsorption Properties of Crystal Violet Dye

Adsorption is one of the effective methods of treating dye wastewater. However, the selection of suitable adsorbent materials is the key to treating dye wastewater. In this paper, GO-ATP was prepared by an intercalation method by inserting graphene oxide (GO) into the interlayer of alabaster attapulgite (ATP), and GO-ATP@CS-PVA aerogel was prepared by co-blending-crosslinking with chitosan (CS) and polyvinyl alcohol (PVA) for the adsorption and removal of crystalline violet dye from the solution. The physicochemical properties of the materials are characterized by various methods. The results showed that the layer spacing of the GO-ATP increased from 1.063 nm to 1.185 nm for the ATP, and the specific surface area was 187.65 m²·g^-1, which was 45.7% greater than that of the ATP. The FTIR results further confirmed the success of the GO-ATP intercalation modification. The thermogravimetric analysis (TGA) results show that the aerogel has good thermal stability properties. The results of static adsorption experiments show that at 302 K and pH 9.0, the adsorption capacity of the GO-ATP@CS-PVA aerogel is 136.06 mg·g^-1. The mass of the aerogel after adsorption-solution equilibrium is 11.4 times that of the initial mass, with excellent adsorption capacity. The quasi-secondary kinetic, Freundlich, and Temkin isotherm models can better describe the adsorption process of the aerogel. The biobased composite aerogel GO-ATP@CS-PVA has good swelling properties, a large specific surface area, easy collection and a low preparation cost. The good network structure gives it unique resilience. The incorporation of clay as a nano-filler can also improve the mechanical properties of the composite aerogel.

Efficient Removal of Methylene Blue by Bio-Based Sodium Alginate/Lignin Composite Hydrogel Beads

Dye pollution is a serious issue in current environment protection, and bio-based adsorbents have been receiving much attention in wastewater treatment, due to their low cost, renewable, and environmentally friendly characteristics. Bio-based sodium alginate/lignin composite (SA/Lig) hydrogel beads were fabricated by a facile cross-linking with calcium ion and used for the removal of methylene blue (MB). The obtained SA/Lig microbeads were characterized with SEM, FTIR, and TG, and the effect of lignin content, pH, and temperature on the MB adsorption was investigated. The results indicated that the introduction of aromatic lignin can not only enhance thermal stability but also can improve the adsorption performance. Under optimal conditions, the maximum adsorption capacity (254.3 mg/g) was obtained for the SA/Lig-20% beads, with a removal efficiency of 84.8%. The adsorption process for MB is endothermic, and the rate-limiting step is chemical adsorption. The removal efficiency is higher than 90% after five cycles, revealing that the prepared beads show good regeneration ability.

Ecofriendly Biosorbents Produced from Cassava Solid Wastes: Sustainable Technology for the Removal of Cd2+, Pb2+, and Crtotal

This research is aimed at investigating the possible use of cassava agroindustry solid wastes in manufacturing adsorbents and their use in removing heavy metals Cd2+, Pb2+, and Crtotal from water. Thus, a pilot study was conducted in two main steps: (1) obtaining and characterizing the adsorbents and (2) laboratory studies focused on the evaluation of critical physicochemical parameters on adsorption, such as pH of the solution containing heavy metals, the effect of adsorbent dose, besides kinetics and equilibrium adsorption and desorption studies. Three adsorbents were studied, cassava barks, bagasse, and their mixture. SEM, FTIR, pHPZC, acid digestion, and chemical composition analysis were employed for adsorbent characterization. The pH of the contaminated solution was evaluated within 4.0 to 7.0, while the adsorbent doses varied from 5.0 to 24.0 g L-1. The adsorption kinetics was evaluated within 5 to 180 minutes and interpreted using pseudofirst- and second-order models. Finally, equilibrium and desorption studies were performed by evaluating adsorbent performance within 5 to 200 mg L-1 of heavy metals, using several nonlinear models for results interpretation. SEM analysis reveals a heterogeneous structure full of cavities. FTIR before and after adsorption reveals gaps related to missing functional groups, suggesting a significant role of alkenes, carboxylic acid, alcohol, anhydride, and ether. pHPZC is found at pH 6.02, 6.04, and 6.26 for adsorbents derived from barks, bagasse, and their mixture. In low concentrations of metals, the higher adsorption capacities were found at pH 7.0 (94.9%) using 16 g L-1 of adsorbent, with the most cost-benefit dose found using 8.0 g L-1. The removal of metals reaches equilibrium within 5-10 minutes of contact time with pseudosecond-order best adjustments to the observed phenomena. The adsorption of metals by a cassava adsorbent is better adjusted to the Freundlich model, with significant and critical information provided by Sips, Redlich-Peterson, Temkin, Liu, and Khan models. Adsorption/desorption studies indicate that cassava adsorbent performs, on average, -10% of the adsorption of metals compared to activated carbon. Nevertheless, factors such as low cost and availability favor the use of such natural materials.

Fabrication of Highly Porous Polymeric Nanocomposite for the Removal of Radioactive U(VI) and Eu(III) Ions from Aqueous Solution

In the present study, a polymeric nanocomposite, CoFe2O4@DHBF, was fabricated using 2,4 dihydroxybenzaldehyde and formaldehyde in basic medium with CoFe2O4 nanoparticles. The fabricated nanocomposite was characterized using FTIR, TGA, XRD, SEM, TEM, and XPS analyses. The analytical results revealed that the magnetic nanocomposite was fabricated successfully with high surface area 370.24 m2/g. The fabricated CoFe2O4@DHBF was used as an efficient adsorbent for the adsorption of U(VI) and Eu(III) ions from contaminated water. pH, initial concentration, adsorption time, and the temperature of the contaminated water solution affecting the adsorption ability of the nanocomposites were studied. The batch adsorption results exposed that the adsorption capacity for the removal of U(VI) and Eu(III) was found to be 237.5 and 225.5 mg/g. The adsorption kinetics support that both the metal ions follow second order adsorption kinetics. The adsorption isotherm well fits with the Langmuir adsorption isotherm and the correlation coefficient (R2) values were found to be 0.9920 and 0.9913 for the adsorption of U(VI) and Eu(III), respectively. It was noticed that the fabricated nanocomposites show excellent regeneration ability and about 220.1 and 211.3 mg/g adsorption capacity remains with U(VI) and Eu(III) under optimum conditions.

Fabrication of starch-salicylaldehyde based polymer nanocomposite (PNC) for the removal of pollutants from contaminated water

In the present study, we have fabricated magnetic nanocomposite based on the starch and salicylaldehyde resin embedded with magnetic Fe₃O₄ nanoparticles (SS@Fe₃O₄). The fabricated nanocomposite was characterized using various analytical methods including XRD, SEM, FTIR, TGA, TEM, BET and XPS. As-fabricated nanocomposite was used for the adsorption of Pb(II) and Cd(II) from aqueous solution. The adsorption results revealed that the maximum adsorption capacity was found to be 265.4 and 247.2 mg/g for Pb(II) and Cd(II) respectively at pH 6 and room temperature. The adsorption kinetic results support that the adsorption of both the toxic metals was carried out via second order reaction and the rate constants were found to be 6.31 × 10^-5 and 7.18 × 10^-5 g·mg^-1·min^-1 for Pb(II) and Cd(II) respectively. The adsorption isotherm displays the Langmuir adsorption isotherm and supports the monolayer and mainly chemisorption with poor physisorption. Additionally, the thermodynamic parameters were evaluated and the adsorption came true in exothermically and spontaneously with both Pb(II) and Cd(II). As-fabricated starch based magnetic nanocomposite displays excellent adsorption as well as outstanding reusability. Therefore, these outcomes support that the SS@Fe₃O₄ nanocomposite can be used as a promising adsorbent for industrial application.