Application of amino-hypophosphite polyampholyte for purification of wastewater containing Ni(ii) ions.

This study investigated the sorption of Ni(ii) ions from an aqueous solution using novel, synthetic amino-hypophosphite polyampholyte resin (AHP) in a batch adsorption system. The removal of Ni(ii) ions was determined as a function of pH (2.0-8.0), initial concentration of Ni(ii) ions (2.0-20.0 mM), resin dosage (1.0-10.0 g dm-3), contact time (0.04-24 h), and temperature (298-318 K). Moreover, continuous fixed-bed column sorption was also studied using model solutions and actual wastewater from the galvanising plant. The batch sorption experimental data showed that the maximum pH for efficient Ni(ii) ion removal was about 5.0. An equilibrium was reached after about 24 hours. The kinetics results were fitted using pseudo-first-order (PFO), pseudo-second-order (PSO), liquid film (LFD), and intraparticle diffusion (IPD) models. Freundlich and Langmuir isotherm models were applied for sorption equilibrium data. The maximum sorption capacity was obtained from the Langmuir equation to be 2.39, 2.52, and 2.62 mmol g-1 at 298, 308, and 318 K, respectively. The thermodynamic parameters for the sorption of Ni(ii) ions on AHP imply the endothermic and spontaneous character of the process. The experimental results demonstrated that amino-hypophosphite polyampholyte resin could be used to effectively remove Ni(ii) ions from model solutions and real wastewater.

Copper(II) ions removal from model galvanic wastewater by green one-pot synthesised amino-hypophosphite polyampholyte.

The amino-hypophosphite polyampholyte (AHP) obtained from cheap and safe building blocks lacks a typical ion-scavenger matrix derived from crude-oil intermediates like poly(divinylbenzene), which is an advantage to commercial solutions. AHP is characterised by sorption capacity comparable to some ion scavengers available on the market, as it was found that its maximum capacity in the temperature range from 298 K to 328 K varies between 114 and 146 mg Cu(II) g-1 of dry AHP. The possible application of the AHP in the Cu(II) removal process from galvanic effluent was investigated. The results show that it is possible to achieve a good removal rate for model wastewater. The inlet Cu2+ concentrations of model wastewater were 6.4 mg Cu(II) dm-3 and 36,2 mg Cu(II) dm-3, acidic and basic galvanic wastewater respectively. After the removal process concentrations were lowered to 1.3 mg Cu(II) dm-3 and 5.1 mg Cu(II) dm-3, for acidic and basic galvanic wastewater respectively. It was found that the presence of Ca(II) and Na(I) did not significantly influence the Cu(II) removal process. The obtained results indicate that the prepared more environmentally safe ion scavenger can be applicable in a wide range of metal ion removal processes.

A review of polyampholytic ion scavengers for toxic metal ion removal from aqueous systems.

Pollution by heavy metal ions in aqueous systems gained researchers attention gradually. Toxic metal ions were always present in the environment and the living organisms could get used to specific concentrations of contaminants with given time, however, sudden concentration rise we are observing can make it impossible for the living organisms to adapt. Many ion removal technologies were developed and optimised over the years to cope with this problem, including chemical precipitation, adsorption, membrane filtration and ion-exchange. Adsorption and ion exchange are processes that employ certain materials, that can be collectively named ion scavengers, to remove ions from aqueous solutions. Some of the scavenger materials are still barely studied, in particular polyampholytes - polymeric zwitterionic materials. This review showcases papers published on toxic metal ion removal by polyampholytes, both commercial and experimental, over last two decades. Many recent publications show promising properties of experimental materials that match or even outperform commercial scavengers. This review was prepared to encourage other researchers to investigate this broad and still not well-studied class of materials especially in context of their ion-scavenging properties. Polyamphytes which may be especially worth the attention and further research have been highlighted as literature studies show that the most unexplored materials in the class of polyamphytes are those containing aminomethylphosphonate, aminomethylsulfonate or hypophosphorous acid group.

Comparison of Cr(VI) Adsorption Using Synthetic Schwertmannite Obtained by Fe3+ Hydrolysis and Fe2+ Oxidation: Kinetics, Isotherms and Adsorption Mechanism.

Good sorption properties and simple synthesis route make schwertmannite an increasingly popular adsorbent. In this work, the adsorption properties of synthetic schwertmannite towards Cr(VI) were investigated. This study aimed to compare the properties and sorption performance of adsorbents obtained by two methods: Fe3+ hydrolysis (SCHA) and Fe2+ oxidation (SCHB). To characterise the sorbents before and after Cr(VI) adsorption, specific surface area, particle size distribution, density, and zeta potential were determined. Additionally, optical micrographs, SEM, and FTIR analyses were performed. Adsorption experiments were performed in varying process conditions: pH, adsorbent dosage, contact time, and initial concentration. Adsorption isotherms were fitted by Freundlich, Langmuir, and Temkin models. Pseudo-first-order, pseudo-second-order, intraparticle diffusion, and liquid film diffusion models were used to fit the kinetics data. Linear regression was used to estimate the parameters of isotherm and kinetic models. The maximum adsorption capacity resulting from the fitted Langmuir isotherm is 42.97 and 17.54 mg·g-1 for SCHA and SCHB. Results show that the adsorption kinetics follows the pseudo-second-order kinetic model. Both iron-based adsorbents are suitable for removing Cr(VI) ions from aqueous solutions. Characterisation of the adsorbents after adsorption suggests that Cr(VI) adsorption can be mainly attributed to ion exchange with SO42- groups.