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The conventional adsorbent fabrication methods involve complicated processes and may cause secondary contaminations. Therefore, an effective eco-friendly method is required for the fabrication of heavy metal adsorbents using inexpensive and eco-friendly materials without secondary pollution during their process. In this study, nanofibrous membranes (NFMs) were fabricated via green electrospinning of poly(vinyl alcohol) (PVA), a hydrophilic polymer, and their water resistance was improved through simple heat treatment without using additional additives. Then, nanofibrous heavy metal adsorbents were prepared by dip-coating the NFMs in an aqueous solution of tannic acid (TA), a natural polyphenol. First, the adsorption/desorption behavior of TA on PVA NFMs during the TA coating process was investigated. In addition, the effects of TA coating on the mechanical properties and heavy metal adsorption characteristics of the PVA NFMs were analyzed. The TA coating significantly increased the mechanical strength, heat resistance, and heavy metal (Pb(II)) adsorption capacity of the PVA NFM. The Pb2+ adsorption amount of TA-coated PVA NFMs exhibited about 5–7 times higher than those of other heavy metal ions, indicating excellent selectivity for Pb2+. In addition, the TA-coated PVA NFMs retained >70% of its initial adsorption capacity even after four cycles of adsorption/desorption, indicating its reusability. [Display omitted] • PVA nanofibrous membrane (NFM) was prepared via green electrospinning. • Tannic acid (TA) coating improved the mechanical strength of PVA NFM by about 5 times. • TA-coated PVA NFM showed excellent adsorption capacity and selectivity for Pb2+. • TA-coated PVA NFM can be applied as a cost-effective and eco-friendly heavy metal adsorbent. [ABSTRACT FROM AUTHOR]

Treating the effluents from industries by using biological and agricultural wastes is an emerging field of research. In this study, three different biosorbents are prepared from tamarind seeds such as; raw, sulphuric acid-modified and ultrasonic-assisted surface-modified tamarind seed powder has been utilized to expel the Pb (II) ions from synthetic solution. The surface characteristics of the newly synthesized raw and surface modified agro-waste biomass were studied by FTIR and SEM. An experimental study was carried out to investigate the effect of different parameters on adsorption of Pb(II) ions using raw, sulphuric acid-modified and ultrasonic-assisted surface-modified tamarind seeds. The maximum Pb(II) ions adsorption was found at pH - 6.0, temperature - 303 K, biosorbent dosage - 3.5 g/L and contact time - 60 min for raw tamarind seeds and 30 min for sulphuric acid-modified and ultrasonic-assisted surface-modified tamarind seeds. The adsorption mechanism was described by Langmuir isotherm and pseudo-first order kinetic model. Among the three biosorbents, ultrasonic-assisted surface-modified tamarind seeds show higher adsorption capacity (18.86 mg/g) of Pb(II) ions removal from the synthetic solution. The thermodynamic study declared that the present Pb(II) ions adsorption onto the prepared biosorbents was spontaneous, exothermic and followed physical adsorption process. Results have shown that tamarind seed was found to be the best adsorbent in the expulsion of Pb(II) ions from the wastewater environment. • Tamarind seeds was utilized as low-cost biosorbent for Pb(II) ions adsorption. • Ultrasonic waves are adopted to improve the surface properties of agro-waste. • The maximum adsorption capacity of UATS was found to be 18.86 mg/g. • Langmuir and pseudo-first order models showed good fit to the Pb(II) ion adsorption. • Biosorption of Pb(II) ions onto RTS, SMTS and UATS are follows physisorption mechanism. [ABSTRACT FROM AUTHOR]

Cassia fistula seeds has been utilized for the abstraction of Pb(II) ions from the aqueous environment. Raw Cassia fistula seeds (RCF) and three different surface modified (physically treated – PMCF and chemically treated – HMCF and SMCF) adsorbent material were taken for investigation. The adsorption properties of these materials and their contact amongst the Pb(II) ion and sorbent materials were characterized by FTIR and SEM analysis. The parameters influencing the adsorption capacity of varied adsorbents were evaluated: maximum solution pH for Pb(II) is 5.0; interactive time is 30 min; dosage is 8.0 g/L for RCF, 4.0 g/L for HMCF, 2.5 g/L for PMCF and 1.0 g/L for SMCF. The modelling study reveals that Freundlich isotherm and Pseudo first order kinetics fits well and the utmost adsorption measurements for the varied adsorbents were found to be 13.22, 28.28, 48.66 and 129.3 mg/g, respectively. [Display omitted] • The performance of RCF, HMCF, PMCF and SMCF for Pb(II) ion was elucidated. • Potential of adsorbents were characterized for Pb(II) ions removal. • The isotherm calculations indicated that Freundlich model was best obeyed. • Thermodynamic investigations confirmed the exothermic nature. [ABSTRACT FROM AUTHOR]

Adsorption of Pb(II) ions in aqueous systems by newly developed mixed biomass has been explored. Mixed biomass was prepared from agro-waste (raw Banyan tree bark, RBTB) and bacterial biomass (Pannonibacter phragmitetus). Chemical modification by sulphuric acid treatment of raw banyan tree bark (SMBTB) was accomplished for the effective separation of toxic Pb(II) ions from the aquatic system. FTIR, SEM and EDX analysis was utilized to deduce sorption characteristics of mixed biomass. Pb(II) ions maximal removal has occurred at pH-6.0, lead (II) ions concentration-25 mg/L, time and mixed biomass dosage (60 min and 3.5 g/L for RBTB – Pannonibacter phragmitetus ; 30 min and 1.5 g/L for SMBTB – Pannonibacter phragmitetus) and temperature (30 °C). Data from equilibrium isotherm and kinetic analysis was best suited to the Langmuir model and pseudo-first-order kinetics. The spontaneous and exothermic nature of Pb(II) ions removal was described by thermodynamic parameters. The mixed biomass proved to be an effective and potential mixed biosorbent for toxic lead removal from solutions. • Agro waste biomass showed that low cost and effective adsorbent. • Sulphuric acid modification enhances the adsorption capacity. • Langmuir isotherm and Pseudo-first-order kinetics showed better fit. • Adsorption of Pb(II) ion was spontaneous and thermodynamically exothermic. [ABSTRACT FROM AUTHOR]