Recovery of Heavy-Metal-Anion Utilizing <i>N,N</i>-Dimethylaminopropylacrylamide/Acrylamide Gels

Abstract

In the present study, in order to examine the N,N-dimethylaminopropylacrylamide/acrylamide {DMAPAA/AAm} hydrogels' capabilities of repetitive heavy-metal-anion recovery from waste fluid, the authors performed successive Cr(VI) adsorption and the adsorbed-Cr(VI) desorption experiments. It has been proved that the DMAPAA/AAm gels show both of the high Cr(VI)-capturing functionality and Cr(VI)-desorption efficiencies. The results in the present study have demonstrated a possibility of a heavy-metal-anion recycling system in which the hydrogels are reused a number of times.

Recovery of Heavy-Metal-Cation Utilizing Sodium acrylate/Acrylamide and <i>p</i>-Styrenesulfonicacidsodiumsalt/Acrylamide Gels

“…As mentioned in the introduction, the authors have been investigating the heavy-metal adsorption and desorption properties of hydrogels [5][6][7][8][9] in order to create new environment purifying materials and to devise new processes which can resolve the current social problems on both the landfillsite-depletion and the heavy-metal-resource drain. The authors have considered that ideal heavy-metal recovery materials should be also recyclable themselves from the viewpoint of the resource saving and reduction of waste generation, which requires the regeneration of the adsorbent after use.…”

“…The authors have observed high heavy-metal-ion capturing efficiencies of some ionized-hydrogels in the previous studies [5][6][7][8][9]: for example, the heavy-metal cation-capturing efficiency of poly(acrylamide/sodium acrylate) (PAAm/SA) gel is estimated ~20wt% of network polymer [5]. The hydrogel which adsorbs heavy-metal cation can be also made with a biodegradable material such as sodium carboxymethylcellulose (CMC-Na) by irradiating γ-ray instead of usually used toxic cross-linker; its heavy-metal-cation capturing efficiency is comparable to the PAAm/SA gel [5].…”

“…After these procedure, Ni(II) concentration and volume of each the remainder solution in the cell was studies [6][7][8][9], the authors adopted this description to express definitely the amount of the p-SSAS, SA and AAm in the respective gels because the p-SSAS/AAm and SA/AAm gels expand in different degrees with the p-SSAS or SA composition ratio to AAm in the rinsing procedure in pure water. These experimental results demonstrate that the p-SSAS and SA work sufficiently as a heavy-metal cation capturer in polymer network of the p-SSAS/AAm and SA/AAm copolymer gels as observed in the previous study [5]: Roughly speaking, the captured Ni(II) amount increases with p-SSAS or SA fraction, however the capturing amount shows a moundlike dependence on the total concentration with a summit around 1.4 M. Besides, having a good look at the p-SSAS-or SA-molar-ratio dependences, the increases in the adsorbed Ni(II) amounts become saturated in the higher p-SSAS-, SA-molar-ratio and total concentration regions.…”

“…The hydrogel which adsorbs heavy-metal cation can be also made with a biodegradable material such as sodium carboxymethylcellulose (CMC-Na) by irradiating γ-ray instead of usually used toxic cross-linker; its heavy-metal-cation capturing efficiency is comparable to the PAAm/SA gel [5]. The authors have been also developing heavy-metal anion capturing gels [6][7][8][9] and found that almost of their heavy-metal capturing efficiencies are larger than those of PAAm/SA and CMC-Na gels and much larger than those of zeolites and ion-exchange resins As mentioned above, some hydrogels can effectively capture hazardous heavy metals. One of the principal ingredients of the high heavy-metal-capturing efficiency can be due to the light elements composing the hydrogels such as H, C, N and O, by which the weight of the adsorbent, namely the hydrogels, becomes very small compared with the inorganic absorbents in the same volume of inorganic adsorbents such as zeolites.…”

Capturing of Positive and Negative Rare-metal Ions by Polarity-Composite Hydrogels

“…In the authors' previous studies, measured were the heavy metal capturing efficiencies both of the positively [9,10,17,18,21] and negatively [11][12][13][14][15][16][19][20][21] ionized hydrogels: The heavy-metal cation capturing efficiency of sodium acrylate/acrylamide (SA/AAm) and carboxymethylcellulose (CMC-Na) gels were found to be ~20 wt% of network polymer [9] [10,21]. As for the heavy-metal-anion capturing hydrogels [11][12][13][14][15][16][19][20][21], their capturing efficiencies are larger than those of SA/AAm and CMC-Na gels, which are much larger than those of zeolites and ion-exchange resins.…”