Insight into the impact of environmental factors on heavy metal adsorption by sodium alginate hydrogel: Inspiration on applicable scenarios.

Sodium alginate (SA) emerges as a promising adsorbent for the remediation of heavy metal-polluted wastewater. However, the systematic investigations on how and the extent to which the various compositions in real water matrices impact its performance were essential but rare when considering its use. Here, we explored the effect of common environmental factors on Cu(II) adsorption by an as-synthesized SA-based hydrogel (SAH). The result showed that high concentration of organics (above 10 mg L-1) had a negative influence on heavy metal removal (decreased by 9.45 % at least), while inorganic ion, turbidity and antibiotics at relatively low concentrations exhibited a negligible even promoting effect (increased by 9.8 % with the presence of 5 mg L-1 Nor). Based on above results and corresponding mechanism analyses, the possible applicable and unsuitable scenarios of SAH can be predicted. SAH could be a great candidate for treating heavy metal-polluted water such as river and lake water, while it is not a good option for electroplating or livestock wastewater which contains high concentration of organic matters. Besides, the operating conditions including pH (5.0 for Cu(II), 6.0 for Ni(II)), contact time (24 h), temperature (298 K) et al. were also determined. Overall, this work provides theoretical guidance and operational strategies for promoting the practical application of SA adsorbent in water treatment.

Adsorption of ionic contaminants from complex water matrices by versatile chitosan-based beads.

Most adsorbents are currently restricted by their single function in pollutant removal from complex wastewater. Herein, we constructed a versatile chitosan-based adsorbent (MC-DA) by grafting amphoteric copolymers with high pH-responsiveness property, aiming at the removal of multiple ionic contaminants. Specifically, the surface charge and hydrophobicity/hydrophilicity of MC-DA can be finely tuned under different pH conditions. As a result, the effective adsorption of cationic methylene blue (MB) and anionic Acid Orange 7 (AO7) with capacities of 627.4 mg/g and 1146.8 mg/g were achieved respectively, superior to most reported materials. Regarding the characterization results, the adsorption mechanisms for MB adsorption were electrostatic and hydrophobic interactions, while the electrostatic attraction was the main driving force for AO7 adsorption. Apart from the versatile adsorption performance, high acid resistance (pH ≥ 2.0), good reusability and rapid separation property under an external magnetic field suggested MC-DA's promising environmental benefits and practical application potential in water remediation.

Macro-manufacturing robust and stable metal-organic framework beads for antibiotics removal from wastewater.

Metal-organic frameworks (MOFs) have shown great prospects in wastewater remediation. However, the easy aggregation, difficult separation and inferior reusability greatly limit their large-scale application. Herein, we proposed a facile, green and low-cost strategy to construct robust and stable MOF-based hydrogel beads (Fe-BTC-HBs) in a gram scale, and employed them to remove antibiotics from wastewater. As a result, the Fe-BTC-HBs demonstrated outstanding adsorption capacity for both ofloxacin (OFL) and tetracycline (TC) (281.17 mg/g for OFL and 223.60 mg/g for TC) under a near-neutral environment. The main adsorption mechanisms of OFL and TC were hydrogen bonding and π-π stacking interaction. Owing to its macroscopic granule and stable structure, Fe-BTC-HBs can be separated rapidly from wastewater after capturing antibiotics, and more than 85% adsorption capacity still remained after six cycles, while the powdered Fe-BTC only showed less than 6% recovery efficiency with massive weight loss (around 92%). In real industrial effluent, the adsorption performance of Fe-BTC-HBs toward two antibiotics exhibited negligible decreases (2.9% for OFL and 2.2% for TC) compared with that in corresponding solutions. Furthermore, Fe-BTC-HBs also had appealing economic and environmental benefit. Overall, the macro-manufactured MOF beads have the promising potential for the large-scale wastewater treatment.