Department of Polymer Science and Technology, University of Calcutta 92, A.P.C. Road, Kolkata 700009, India.
Department of Polymer Science and Technology, University of Calcutta 92, A.P.C. Road, Kolkata 700009, India.
Carbohydr Polym. 2020 May 15;236:116055. doi: 10.1016/j.carbpol.2020.116055. Epub 2020 Feb 21.
An elastic semi IPN from guar gum (GG), xanthan gum (XG) and poly(acrylic acid) (PAA) was developed and used as a bioadsorbent for soluble Pb(II) and Hg(II) from water. The IPNs were developed using a photo-initiated crosslinking cum polymerization approach (benzophenone was used as an initiator) with a variable composition of the biopolymers (GG:XG fixed at 20:80 by mass) to PAA by mass (Biopolymers: PAA as 90:10, 80:20, 70:30 and 50:50, respectively). The hybrids were extensively characterized for microstructure, morphology, swelling, porosity and rheological behavior, both in dry and swelled conditions. Three grades of biosorbents namely 90:10, 80:20 and 70:30 showed an enhanced adsorption efficiency compared to the remaining ternary grades as well as the crosslinked binary grade of GG:XG (20:80 mass composition, used as a control), respectively. It was primarily due to high network strength (elasticity) cum flexibility (more liquid like behavior) of those three ternary grades under swollen condition followed by their higher swelling capacity and strongly negative zeta potential to attract the positively charged Pb(II) and Hg(II), respectively. The 80:20 grade (80 parts was the mass composed of XG:GG in 80:20 mass ratio and 20 parts was the mass of PAA) exhibited the maximum molecular effect and thus recorded the highest adsorption efficiency (93 % for Pb(II) with an adsorption capacity of 111.6 and 72 % of Hg(II) with an adsorption capacity of 86.4). Nevertheless, all the hybrids showed a strong pH dependant adsorption as the -COOH unit present in the network displayed a pH sensitive ionization. The adsorption was lower below the pH level of 4.0 (pKa of PAA at 4.5) while drastically improved beyond that. On additional note, the adsorbate dose was also found to affect the adsorption efficiency whereby a maximum dose of 300 ppm of both Pb(II) and Hg(II) was found to be most effective for adsorption.
从瓜尔胶（GG）、黄原胶（XG）和聚丙烯酸（PAA）开发了一种弹性半互穿网络（semi IPN），并将其用作水中可溶性 Pb(II) 和 Hg(II) 的生物吸附剂。该互穿网络是通过光引发交联聚合方法（使用苯甲酮作为引发剂）开发的，其中生物聚合物（GG:XG 按质量比固定在 20:80）与 PAA 的质量比为（生物聚合物：PAA 分别为 90:10、80:20、70:30 和 50:50）。对混合物的微观结构、形态、溶胀、孔隙率和流变行为进行了广泛的表征，包括在干燥和溶胀条件下。与剩余的三元等级以及作为对照的交联二元 GG:XG（20:80 质量组成）相比，三种等级的生物吸附剂（90:10、80:20 和 70:30）表现出更高的吸附效率。这主要是由于在溶胀条件下，这三种三元等级具有较高的网络强度（弹性）和灵活性（更像液体的行为），随后它们具有更高的溶胀能力和强烈的负 zeta 电位，分别吸引带正电荷的 Pb(II) 和 Hg(II)。80:20 级（80 部分是 XG:GG 按 80:20 质量比组成的质量，20 部分是 PAA 的质量）表现出最大的分子效应，因此记录了最高的吸附效率（93%的 Pb(II)，吸附容量为 111.6，72%的 Hg(II)，吸附容量为 86.4）。然而，所有的混合物都表现出强烈的 pH 依赖吸附，因为网络中的 -COOH 单元表现出 pH 敏感的离子化。在 pH 水平低于 4.0（PAA 的 pKa 值为 4.5）时，吸附作用较低，而超过该 pH 值时，吸附作用则急剧提高。此外，还发现吸附剂剂量也会影响吸附效率，发现对于吸附，最佳剂量为 300ppm 的 Pb(II) 和 Hg(II)。
