Adsorbents For Water Remediation Research Articles

Scottish softwood biochar for water remediation targeting selected persistent organic pollutants

A Scottish wood biochar sample was investigated for water remediation against persistent organic pollutants as a potential renewable material for adsorption processes. Textural characterisation gave a high surface area (588 m2/g) and a mix of microporous and mesoporous nature with an average pore width of 4 nm. Morphological analysis revealed a layered carbon structure and spectroscopic analysis showed the presence of oxygen and nitrogen-based functionalities alongside 80% atomic carbon. The biochar had an average point of zero charge of 7.44 ± 0.2. 3,4-Dichloroaniline kinetic rates were rapid (<5 min), restricting kinetic analysis, while a pseudo-second-order kinetic model was best suited to represent the kinetic data for acetaminophen and carbamazepine, suggesting chemical control. The adsorption equilibria were most appropriately described by the Sips isotherm model, further supporting the chemical control theory for a multilayer system. Maximum adsorption capacity was 126 mg/g for acetaminophen removal, 40 mg/g for carbamazepine and 83 mg/g for 3,4-dichloroaniline. The biochar demonstrated good removal efficiency against all target species, showing potential as an adsorbent for water remediation.

Natural and Synthetic Fiber‐Based Adsorbents for Water Remediation

AbstractThe use of unmodified and chemically treated natural fibers for water remediation (removal of chemical residues/oil spills and organic wastewater from water) is a significant and low‐cost strategy to reduce the contamination of aquifers with metal ions, as well as marine environments with oil spills and water bodies with organic dyes. Furthermore, synthetic fibers exhibit a superior performance owing to their tunable surface area and superhydrophobic/swelling properties. This review summarizes the most recent advances in natural fiber‐based biosorbents and synthetic fiber mats since the efficient removal of toxic compounds depend on adequate incorporation of functional groups on the fiber surface for mutual electrostatic and diffusion of contaminants into the fibrils. The most relevant results in the removal of oil, trace metal ions, and organic dyes are presented and evaluated. The evaluation is done according to the strategies for chemical modification of raw materials by the reuse of plastics or conventional electrospinning techniques to support the hierarchical growth of more complex chemical structures.

Lignin-based few-layered graphene-encapsulated iron nanoparticles for water remediation

• Few-layered graphene-encapsulated iron nanoparticles (FLG@Fe0) supported on lignin-based carbon (LC) were synthesized. • The ‘few-layered’ graphene shell protects the zero-valent iron core from fast passivation. • LC-FLG@Fe 0 exhibited superior performance for uptake Pb(II), As(III), phosphate, and nitrate from aqueous solutions. • The removal mechanisms of LC-FLG@Fe 0 for Pb(II), As(III), phosphate, and nitrate were proposed. The potential of iron nanoparticles as adsorbents for water remediation has not been fully exploited because of their intrinsically low stability. Herein, few-layered graphene-encapsulated iron nanoparticles (FLG@Fe 0 ) supported on and within lignin-derived carbon were synthesized via an in-situ thermal conversion of ferric nitrate-loaded kraft lignin, i.e. , ferric nitrate as a Fe source and lignin as a carbon source. The structure and morphology analyses indicated that these lignin-based FLG@Fe 0 particles sized 5–15 nm in diameter were composed of nanoscale zero-valent iron (nZVI) cores shelled with 1–3 graphene layers. The ‘few-layered’ graphene shell protects nZVI cores from fast passivation. The lignin-derived carbon support prevents the FLG@Fe 0 sites from agglomeration. These two features can enhance the stability and applicability of FLG@Fe 0 for water remediation. Consequently, these lignin-based FLG@Fe 0 particles exhibited superior uptake capacities of 127.5, 107.2, 214.7, and 356.8 mg/g for Pb(II), As(III), phosphate, and nitrate, respectively. The removal mechanism analyses indicated that precipitation, redox reaction, and catalytic degradation were involved. This versatile lignin-derived carbon-supported FLG@Fe 0 particles (LC-FLG@Fe 0 ) could be a promising renewable adsorbent for offering green and economic alternatives to conventional nZVI adsorbents synthesized using hazardous and expensive NaBH 4 process.

Calcium Alginate Beads Doped with Nano-ZrO2 and Activated Carbon of Annona reticulate Plant as an Effective Adsorbent for Water Remediation of Chromium(VI)

An activated carbon produced from stems of Annona reticulate plant (SACAR) by conc. H2SO4 digestion, is observed to have strong affinity for toxic Cr(VI) ions. Its adsorptivity for Cr(VI) ions was enhanced by admixing it with ‘nano-ZrO2’ (Zr-SACAR)-synthesized adopting green methods. For ensuring easy filtration, the ‘active carbon + nanoparticle composite’ was immobilized in calcium alginate beads (Zr-SACAR-Ca). Optimum extraction conditions for these three adsorbents for the removal of Cr(VI) ions from water were investigated. The adsorption capacities were found to be 92.2 mg/g for SACAR; 109.83 mg/g for Zr-SACAR and 119.34 mg/g for Zr-SACAR-Ca. The sorption nature was characterized by XRD, FTIR, FESEM and EDX studies. The sorption mechanism was investigated using various isotherm models. Thermodynamic studies revealed the endothermic and spontaneous nature of sorption. The kinetics of adsorption was well defined by the pseudo-second-order model. The spent adsorbent are regenerated and reused until six cycles with marginal decrease in Cr-adsorptivity. The adsorbents developed are effectively applied in the treatment of polluted water samples collected from Ethiopia

Laboratory Adsorption Studies on Cadmium (II) by Nonwoven Chitosan/Phosphorylated Microcellulose Nanocomposite

The rapid growth of human population and global industrialization has resulted in the generation of larger amounts of wastewater containing various pollutants, among which toxic heavy metals. Adsorption is efficient for this purpose, but its application is limited by the high cost of adsorbent materials. Chitosan (CS) and phosphorylated microcellulose (PMC) have a high potential as low-cost and effective adsorbents for water remediation. Nonwoven CS/PMC nanocomposite fiber mats were produced by electrospinning with up to 50% by weight of PMC. The thermal, chemical, and morphological properties of the mats were studied. Batch adsorption trials were carried out using Cd2+ ions. Kinetics and isotherm models were tested against experimental results and the thermodynamic properties were calculated. Results showed that the pseudo-second order model best fitted experimental data and suggested chemisorption as the mechanism for Cd2+ removal. Langmuir isotherm best described equilibrium data reaching the maximum adsorption capacity of 283 mg/g at 60 °C. This high value was attributed mainly to the large amount of phosphate groups, which require less energy to capture the metal cations. Thermodynamic evaluation suggested that the adsorption is a spontaneous endothermic reaction. These results confirm that CS/PMC mats are easy to produce, and provide high adsorption capacity in simulated wastewater containing Cd2+. These laboratory-based adsorption experiments will assist in selecting/ranking of potential candidate matrices, and scale-up development of technologies for complex wastewater applications.

Efficient waste polyvinyl(butyral) and cellulose composite enabled carbon nanofibers for oxygen reduction reaction and water remediation

Waste polyvinyl(butyral) (W-PVB) collected from the windshields of end-of-life vehicles has drawn considerable interest as a complementary and abundant resource. However, large amounts of W-PVB are still being buried in landfills every year owing to a lack of recycling techniques. As an alternative, we report the fabrication of carbon nanofibers from natural cellulose and W-PVB composites using a facile electrospinning, carbonization, and KOH activation approach. Interestingly, volatiles and residual carbon from a W-PVB matrix through carbonization produce highly porous carbon nanofibers and a defective graphitic surface layer, respectively. As a result of the large surface area (698.1 m2 g−1) and pore volume (0.2919 cm3 g−1) from abundant micropores, as well as the high density of active sites from defects, resulting carbon nanofiber shows a superior performance in environmental applications. It serves as a metal-free and un-doped carbon catalyst with a half-wave potential of 0.76 V vs RHE for the oxygen reduction reaction and a 99.6% removal of rhodamine B from water as an adsorbent for water remediation. This simple strategy can open a new approach to the design and synthesis of various classes of W-PVB-based composites, which will broaden the reuse of W-PVB in renewable and sustainable applications.

Oxidized graphitic carbon nitride nanosheets as an effective adsorbent for organic dyes and tetracycline for water remediation

Graphitic carbon nitride (g-C3N4) is promising as adsorbent for water remediation as its chemical structure allows a variety of mechanisms to interact with wastewater pollutants. However, several issues, such as low specific surface area and insufficient dispersibility in water, have to be tackled to achieve a competitive performance in such use. Previous attempts to improve the features of g-C3N4as an adsorbent have relied on carbon doping and exfoliation in the solid phase by thermal expansion. Here, we demonstrate that exfoliation in the liquid phase by a combination of oxidation and sonication allows preparing g–C3N4–based materials with improved dispersibility in water, increased exposed surface, and abundance of surface functional groups. The obtained oxidized g-C3N4 adsorbents exhibited high adsorption capacities which were remarkable towards organic dyes (∼70–600 mg/g) and excellent in the case of the antibiotic tetracycline (895 mg/g) in aqueous solution. The present results should open new opportunities for the use of oxidized g-C3N4 materials as adsorbents for water remediation.

Nano-structured Cellulose as Green Adsorbents for Water Purification: A Mini Review

Celluloses are natural polysaccharides that have garnered attentions in recent years due to their sustainability, availability and notable applications in various fields. Whilst demand of clean water sources keep increasing, modified nano-structured cellulose derived from agricultural waste showed a good prospect in adsorbing pollutants from water. To date, large number of studies have reported the performance of nanocellulose in removing wide range of pollutants from effluents. The purpose of this mini review is to present an overview of existing literatures on the utilization of nanocellulose-based materials as adsorbent for water remediation and make aware of possible development of integrating adsorption and nanotechnology for water separation and purification.

Polydopamine Nanoparticle-Coated Polysulfone Porous Granules as Adsorbents for Water Remediation.

Water purification technologies possibly based on eco-sustainable, low cost, and multifunctional materials are being intensively pursued to resolve the current water scarcity and pollution. In this scenario, polysulfone hollow porous granules (PS-HPGs) prepared from scraps of the industrial production of polysulfone hollow fiber membranes were recently introduced as adsorbents and filtration materials for water and air treatment. Here, we report the functionalization of PS-HPGs with polydopamine (PD) nanoparticles for the preparation of a new versatile and efficient adsorbent material, namely, PSPD-HPGs. The in situ growth of PD under mild alkaline oxidative polymerization allowed us to stably graft PD on polysulfone granules. Enhanced removal efficiency of ofloxacin, an antibiotic drug, with an improvement up to 70% with respect to the pristine PS-HPGs, and removal of Zn(II) and Ni(II) were also observed after PD modification. Remarkably, removal of Cu(II) ions with an efficiency up to 80% was observed for PSPD-HPGs, whereas no adsorption was found for the PD-free precursor. Collectively, these data show that modification with a biocompatible polymer such as PD provides a simple and valuable tool to enlarge the field of application of polysulfone hollow granules for water remediation from both organic and metal cation contaminants.

Adsorption of two antibiotics on biochar prepared in air-containing atmosphere: Influence of biochar porosity and molecular size of antibiotics

The porous biochar was prepared by pyrolysis of wood at 600–800 °C in the air-containing atmosphere, so as to enhance the biochar's capacity for adsorption of antibiotics from water. The analytical results obtained from N2 adsorption/desorption indicated that air addition in pyrolysis atmosphere improved significantly the biochar's porosity, especially the development of mesopores. The mesoporous biochars showed high adsorption of antibiotics, and the highest adsorption was observed on the A1/5C800 biochar prepared at the air/gas ratio of 1/5 and heat treatment temperature (HTT) of 800 °C. The adsorption isotherm data were well fitted to the Langmuir model, and the maximum adsorptions (Qm) of tetracycline and sulfadiazine on the A1/5C800 sample are 163 and 261 mg/g respectively, which are 18.8 and 52.8 folds of those on the microporous NC800 biochar prepared at the same HTT but in total nitrogen atmosphere. The outstanding performance of mesoporous biochar was linked to the utilization of more inner pore surface for adsorption, which favors the adsorption of smaller-sized sulfadiazine molecules. While the stronger interactions between tetracycline and biochar contributed to the relatively higher adsorption of tetracycline on the microporous biochar. The mesoporous biochar retained most of the adsorption capacity (>50%) in a wide pH range (3.5–10) and with the co-existence of humic acid (10 mg/L). In general, this research provides a simple and green method to enhance the biochar's efficiency as an adsorbent for remediation of water contaminated by antibiotics.