Carboxylmethyl konjac glucomannan conjugated polydopamine composites for Pb(II) removal
Introduction
Heavy metal pollutants are an increasing environmental problem in water contamination. The rapid growth of industrial activities is the main source of the introduction of heavy metal ions into soil and ground water. Lead, considered one of the most harmful pollutants in natural surroundings due to its non-biodegradability, toxicity, and accumulation in living organisms, can have adverse effects on the central nervous system, pulmonary, liver, and kidney functions (Feber and Ahmed, 2010, Feng et al., 2013, Karatas, 2012, Nadeema et al., 2006). Despite the long-term focus on preventing and ameliorating the adverse health effects of lead ion, lead contamination is even increasing in some parts of the world. Lead has been found in industrial effluents such as mining, dyestuff, metal plating, and battery manufacturing drainage (Huang et al., 2015, Kong et al., 2014; Shahbazi, Younesi, & Badiei, 2011).
Common accepted technologies for the removal of lead from wastewater include in situ solidification, ion-exchange, chemical precipitation, membrane filtration, and adsorption (Singha & Guleria, 2014). Among these methods, adsorption has been regarded as an environmentally friendly, simple, effective, and economical alternative method for removal of heavy metals, due to the ease and efficiency with which it can be applied for the treatment of wastewater containing heavy metal (Bilal et al., 2013; Goel, Kadirvelu, Rajagopal, & Garg, 2006; Mondal, 2009, Sargin and Arslan, 2015). Traditional adsorbent materials, including biochar, activated carbon, clay, and natural zeolite, suffer from low efficiency or difficult recovery, with high operational cost in their practical applications because of additional steps such as filtration, magnetic separation, and centrifugation. Thus, it is becoming increasingly important to find a novel adsorbent to remove Pb(II) from wastewater.
In this study, we report the preparation and application of carboxylmethyl konjac glucomannan (CMKGM) functionalized with polydopamine (PDA) for removal of Pb(II) in water purification. As a renewable natural polymer, KGM, which is extracted from amorphous konjak composed of mannose and glucose in a molar ratio of 1.6:1 with a β-1, 4-linkage and contains an acetyl group every 12 or 18 repeating units, exhibits excellent biocompatibility, biodegradability, widely functionalized potential properties, and low-cost (Ratcliffe, Williams, Viebke, & Meadows, 2005; Williams et al., 2000). It also possesses the great advantages of gelling, film-forming, antibacterial action, and low caloric value, facilitating its broad application in the food, chemical, biological, and medical industries. What is more, KGM is a promising adsorbent for the removal of heavy metal, due to the abundance of hydroxyl groups in its polymer chains. However, KGM cannot be used directly as an adsorbent because of its high solubility in aqueous solution. Luo, Liu and Lin (2009) converted KGM into water insoluble konjac glucomannan to absorb Pb(II) by treating with NaOH via completely deacetylated reaction. Niu, Wu, Wang, Li and Wang (2007) prepared crosslinked carboxymethyl konjac glucomannan though reaction of monochloroacetic to absorb Pb2+, Cu2+ and Cd2+ and Chen, Zhang and Li (2016) explored a biodegradable Konjac glucomannan-poly(acrylic acid) hydrogel which was prepared by Konjac glucomannan grafting with acrylic acid to adsorb Cu(II). Thus, chemical modifications of KGM are necessary for removal of heavy metal ions. CMKGM is the carboxymethyl modification of KGM, but it still displays low efficiency for the removal of Pb(II).
Dopamine (DA) is a biogenic catecholamine that presents excellent biocompatibility, spontaneous polymerization and strong adhesiveness, as well as possesses many active groups (Baron, Zayats, & Willner, 2005; Lee, Dellatore, Miller, & Messersmith, 2007; Xu, Sheng, Li , & Shi, 2010; Baron et al., 2005). DA can be spontaneously polymerized into poly(dopamine) (PDA) easily and form an adhesive coating on a substrate in alkaline buffer, and catechol groups on DA are essential to their adhesive functions in wet environments. In addition, nitrogen heteroatoms as well as catechol groups in PDA have a strong tendency that can promote interaction between PDA and metal ions through electrostatic, chelating, or hydrogen bonding interactions (Farnad, Farhadi, & Voelcker, 2012; Ye, Zhou, & Liu, 2011). Thus, DA could serve functional roles as a surface functionalization agent. Here we report the study of CMKGM coated with PDA for Pb(II) removal achieved by combining both the adhesive properties and the metal binding capacities of the PDA to improve the adsorption performance of CMKGM for removal of Pb(II) ion.
We first synthesized a novel carboxylmethyl konjac glucomannan conjugated polydopamine (CMKGM-PDA) bead adsorbent for lead removal from aqueous solution through a simple electronic injection combined with a polymerization method. The present work focuses on the synthesis of CMKGM-PDA bead to remove Pb(II) ion. Batch adsorption experiments were carried out to determine the effects of factors such as the dosage of adsorbent, pH of lead solution, contact time, initial lead ion concentration, and adsorption temperature. Furthermore, we investigated various adsorption isotherms and kinetic models to understand the adsorption process of CMKGM-PDA. Finally, the adsorption mechanism of Pb(II) on CMKGM-PDA was analyzed.
Section snippets
Materials
Dopamine was purchased from Sigma Aldrich, USA. konjac glucomannan (refined flour) was purchased from Mianyang Haomao Konjac Food Co., Ltd. in China. Sodium hydroxide, and hydrochloric acid were purchased from Chengdu Kelong Chemical Reagent Factory Co., Ltd., China. Different concentrations of lead ion were obtained by dissolving certain amounts of Pb(NO3)2 in ultrapure water purchased from Kelong Chemicals, China. Zn(NO3)2·6H2O, Cd(NO3)2·4H2O, Ni(NO3)2·6H2O, Co(NO3)2·6H2O, Cu(NO3)2·3H2O and
General characterization
The morphology of the prepared materials was investigated by SEM-EDX analysis, shown in Fig. 1. The images illustrate that the CMKGM powder was presented with a number of creases that could be attributed to water evaporation and surface shrinking (Fig. 1a), the CMKGM bead was marked by many tiny folds and micropores resulting from the linked role of Fe3+ (Fig. 1b), indicating that the linking process made a contribution to shaping of the adsorbents and densification of the gel particles.
Conclusions
In this study, a simple and effective approach based on surface modification of CMKGM with polydopamine was developed to obtain a CMKGM-PDA adsorbent which demonstrated excellent adsorption of Pb(II). The equilibrium adsorption capacity and the maximum adsorption capacity of CMKGM-PDA were 42.68 and 95.24 mg g−1, respectively, for Pb(II) at 298 K. Moreover, the adsorption capacity increased with an increase in temperature. The adsorption process was consistent with pseudo-second-order kinetic and
Acknowledgements
This research was supported by the National Natural Science Foundation of China (NSFC; Grant No. 31300793, 31400809), Engineering Research Center of Biomass Materials (SWUST), Ministry of Education (No. 13zxbk03).
References (45)
- et al.
Waste biomass adsorbents for copper removal from industrial wastewater – a review
Journal of Hazardous Materials
(2013) - et al.
The adsorption behavior and mechanism investigation of Pb(II) removal by flocculation using microbial flocculant GA1
Bioresource Technology
(2013) - et al.
Adsorptive removal of Pb(II) by magnetic activated carbon incorporated with amino groups from aqueous solutions
Journal of the Taiwan Institute of Chemical Engineers
(2016) Removal of Pb(II) from water by natural zeolitic tuff: Kinetics and thermodynamics
Journal of Hazardous Materials
(2012)- et al.
Adsorption of Pb(II) from aqueous solution using keratin waste hide waste: Equilibrium, kinetic and thermodynamic modeling studies
Chemical Engineering Journal
(2014) - et al.
Preparation of triethylene-tetramine grafted magnetic chitosan for adsorption of Pb(II) ion from aqueous solutions
Journal of Hazardous Materials
(2013) - et al.
Chemical reaction-and particle diffusion-based kinetic modeling of metal biosorption by a Phormidium sp.-dominated cyanobacterial mat
Bioresource Technology
(2011) - et al.
A novel benzimidazole-functionalized 2-D COF material: Synthesis and application as a selective solid-phase extractant for separation of uranium
Journal of Colloid and Interface Science
(2015) - et al.
Simultaneous removal of Pb(II) and 2,4,6-trichlorophenol by a hierarchical porous PU@PDA@MSNs sponge with reversible “shape memory effect
Chemical Engineering Journal
(2016) - et al.
Al-doping chitosan-Fe(III) hydrogel for the removal of fluoride from aqueous solutions
Chemical Engineering Journal
(2014)