Adsorption of metals to membrane filters in view of their speciation in nutrient solution

Abstract

Filtration of a solution may lower metal concentrations through adsorption of metal species to the filter. Processes such as filter-sterilizing nutrient solution and filtration of field water are sensitive to these sorption artifacts, yet basic data on the affinity of different filters for metals are lacking. This article describes the adsorption of five metals to eight types of 0.2-microm membrane filters used for sterilizing a plant (Lemna minor L.) culture medium. Filters of cellulose acetate, cellulose nitrate, mixed cellulose ester, nylon, polyamide, polycarbonate, polyester, and polyvinylidene fluoride were tested for their affinity toward mono- (K), di-(Mn, Cu, Zn), and trivalent (lanthanum [La]) metals. Metal concentrations were quantified using radioisotopes and speciation was calculated. Results showed that metals had the lowest affinity for polycarbonate and nylon filters and the highest affinity for cellulose- and polyester-type filters. Furthermore, it was shown that the metal load on cellulose filters correlated best with free ion concentrations (indicating electrostatic attraction), while loads on other filters correlated better with total metal concentrations. Filtering a 5-ml solution of pH 5 did not affect its metal concentrations, ranging from 10 nM (La) to 49 microM (K). To minimize filtration artifacts, we propose using polycarbonate or nylon filters, especially when dealing with low volumes of high pH and low metal species concentrations.

Solubility and dissimilatory reduction kinetics of iron(III) oxyhydroxides: A linear free energy relationship

“…The dialysis bags were completely submerged and kept in the dark under aerobic conditions in a thermo-stated water bath at 25°C. We chose cellulosic dialysis bags because they exhibit minimal adsorption affinity for di-and tri-valent metallic cations at the pH range considered in our experiments (Farrah and Pickering, 1978;Weltje et al, 2003).…”

Use of filtration techniques to study environmental fate of engineered metallic nanoparticles: Factors affecting filter performance

“…Microfiltration (MF) using 0.45 m cut-off filter membranes is commonly utilized to determine the dissolved metal fraction in e.g., surface waters or soil solutions [7,16], while 0.2 m filtration is routinely used for sterilization of for instance nutrient media [38]. However, solely based on size, nanoparticles should be allowed to permeate during MF due to their extremely small dimensions, thereby ending up in the so-called "dissolved" fraction.…”

“…The membrane-fouling phenomena and other filtration induced artefacts occurring during trace metal analysis have been investigated [13,38,29,16].…”

Systematic evaluation of dissolved lead sorption losses to particulate syringe filter materials

“…They also found that the loss of trace metals (lead and copper, among others) was especially significant after filtering with a 0.45-μm nylon syringe filter. Weltje et al (2003) examined sorption of various metals in nutrient solution onto an array of 0.22-μm membrane filters, including those made of cellulose acetate, cellulose nitrate, mixed cellulose ester, nylon, p o l y a m i d e , p o l y c a r b o n a t e , p o l y e s t e r, a n d polyvinylidene. Using a filter holder, a syringe was used to push the samples through.…”