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Novel Mesoporous Lignin-Calcium for Efficiently Scavenging Cationic Dyes from Dyestuff Effluent.

ABSTRACT: A novel adsorbent lignin-calcium was fabricated by a simple flocculation-sedimentation approach to remove methylene blue. The structure and morphology of the well-prepared sample were analyzed by multiple characterization methods. Lignin-calcium microspheres demonstrated a mesoporous and inserted layer structure with a coarse surface. Methylene blue (MB) adsorption by lignin-calcium complied with the Langmuir model, showing a maximum adsorption amount of 803.9 mg/g, exceeding that reported in the literature by 3-22-fold. The adsorption kinetics matched the pseudo-second-order model well. The pore volume diffusion model was technically applied to evaluate the mass transfer mechanisms. The effective pore volume diffusion coefficient was 6.28 × 10^-12 m²/s. Furthermore, lignin-calcium exhibited excellent adsorbability for methylene blue across a pH range from 3 to 11 and could be regenerated by hydrochloric acid with an elution efficiency of 62.44%. Multiple mechanisms may support the adsorption. Altogether, the tailor-made lignin-calcium is promising as an efficient and sustainable adsorbent for scavenging cationic dyes from dyestuff effluent.

SUBMITTER: Dai K

PROVIDER: S-EPMC7808136 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature

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Novel Mesoporous Lignin-Calcium for Efficiently Scavenging Cationic Dyes from Dyestuff Effluent.

Dai Kun K Zhao Gulin G Wang Zichen Z Peng Xiaoqiang X Wu Jinglan J Yang Pengpeng P Li Ming M Tang Chenglun C Zhuang Wei W Ying Hanjie H

ACS omega 20201229 1

A novel adsorbent lignin-calcium was fabricated by a simple flocculation-sedimentation approach to remove methylene blue. The structure and morphology of the well-prepared sample were analyzed by multiple characterization methods. Lignin-calcium microspheres demonstrated a mesoporous and inserted layer structure with a coarse surface. Methylene blue (MB) adsorption by lignin-calcium complied with the Langmuir model, showing a maximum adsorption amount of 803.9 mg/g, exceeding that reported in th ...[more]

PMID: 33458532

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Project description:In wastewater treatment, flocculation is a widely used solid/liquid separation technique, which typically employs a charged polymer, a polyelectrolyte (PEL). Polyelectrolytes features, such as charge type, charge density and molecular weight, are essential parameters affecting the mechanism of flocculation and subsequent floc sedimentation. The effectiveness of the process is also influenced by the characteristics of the system (e.g., type, size, and available surface area of suspended particles, pH of the medium, charge of suspended particles). Thus, a good understanding of the flocculation kinetics, involved mechanisms and flocs structure is essential in identifying the most adequate treatment conditions, having also into consideration possible subsequent treatments. In this study, Eucalyptus bleached pulp and a cellulosic pulp with high lignin content (~4.5 wt%) obtained from Eucalyptus wood waste were used for bio-PELs production. Firstly, a pre-treatment with sodium periodate increased the pulps reactivity. To produce cationic cellulose the oxidation step was followed by the introduction of cationic groups in the cellulose chains, through reaction with Girard's reagent T. Applying different molar ratios (0.975 and 3.9) of Girard's reagent T to aldehyde groups led to cationic PELs with diverse charge density. On the other hand, to obtain anionic cellulose a sulfonation reaction with sodium metabisulfite was applied to the intermediate dialdehyde cellulose-based products, during 24 or 72 h, and anionic-PELs with diverse features were obtained. The developed water soluble, anionic and cationic bio-PELs were characterized and tested as flocculation agents for a textile industry effluent treatment. Initially, jar-tests were used to tune the most effective flocculation procedure (pH, flocculant dosage, etc.). Flocculation using these conditions was then monitored continuously, over time, using laser diffraction spectroscopy (LDS). Due to the small size of the dyes molecules, a dual system with an inorganic complexation agent (bentonite) was essential for effective decolouration of the effluent. Performance in the treatment was monitored first by turbidity removal evaluation (75-88% with cationic-PELs, 75-81% with anionic-PELs) and COD reduction evaluation (79-81% with cationic-PELs, 63-77% with anionic-PELs) in the jar tests. Additionally, the evolution of flocs characteristics (structure and size) during their growth and the flocculation kinetics, were studied using the LDS technique, applying the different PELs produced and for a range of PEL concentration. The results obtained through this monitoring procedure allowed to discuss the possible flocculation mechanisms involved in the process. The results obtained with the bio-PELs were compared with those obtained using synthetic PELs, commonly applied in effluents treatment, polyacrylamides. The developed bio-PELs can be competitive, eco-friendly flocculation agents for effluents treatment from several industries, when compared to traditional synthetic flocculants with a significant environmental footprint. Moreover, LDS proved to be a feasible technique to monitor flocculation processes, even when a real industrial effluent is being tested.

Project description:The radical polymerization of acid-washed and unwashed softwood kraft lignin with [2-(methacryloyloxy) ethyl] trimethylammonium chloride (METAC) was attempted to investigate the production of lignin-based flocculants for simulated wastewater. The incorporation of METAC onto lignin resulted in a cationic charge density (2.3-3.3 meq/g), increased water solubility (89-96% in neutral pH), and increased molecular weight (70,000-210,000 g/mol) of lignin. The lignin-METAC polymers generated from acid-washed lignin had higher molecular weights than those generated from unwashed lignin. The lignin-METAC polymers showed lower resistance to thermal decomposition than unmodified lignin due to the inclusion of PolyMETAC. The unmodified acid-washed lignin samples did not significantly affect the COD of the wastewater, while the unmodified unwashed lignin samples contributed to the COD, implying that unmodified lignin was not suitable for wastewater treatment. The flocculation of wastewater with lignin-METAC led to the chemical oxygen demand (COD) reduction of 17-23% and total organic carbon (TOC) drop of 51-60%. The lignin-METAC polymer with the highest molecular weight (produced from acid-washed lignin) reached the highest COD removal, while lignin-METAC polymer with the highest charge density (produced from unwashed lignin) reached the highest TOC removal. Focused beam reflectance measurement (FBRM) studies revealed that the lignin-METAC polymer produced from acid-washed lignin with a high molecular weight generated larger and more flocs in wastewater than the lignin-METAC polymer produced from unwashed lignin. The comparison of theoretical and experimental dosages required for neutralizing the charges of wastewater demonstrated that charge neutralization was the main flocculation mechanism, although a bridging mechanism was also involved for component removals from wastewater. The use of 1 mg/L of alum along with 65 mg/L lignin-METAC in a dual coagulation-flocculation system led to higher average phosphorous (42%) and COD (44%) removals than the singular flocculation system only using 65 mg/L of lignin-METAC (with phosphorous removals of 3.4% and COD removals of 18.7%). However, lignin-METAC flocculant slightly increased the ammonia-nitrogen content in both singular flocculation and dual coagulation-flocculation systems due to the residual ammonia content of lignin-METAC. The coagulation-flocculation system determined that the use of lignin-METAC (65 mg/L) could reduce the alum dosage significantly while maintaining a similar organic content reduction of 44% for wastewater.

Dataset Information

Novel Mesoporous Lignin-Calcium for Efficiently Scavenging Cationic Dyes from Dyestuff Effluent.

Publications

Novel Mesoporous Lignin-Calcium for Efficiently Scavenging Cationic Dyes from Dyestuff Effluent.

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