Treatment of metal (loid) contaminated solutions using iron-peat as sorbent: is landfilling a suitable management option for the spent sorbent?

Abstract

This study firstly aimed to investigate the potential of simultaneous metal (loid) removal from metal (oid) solution through adsorption on iron-peat, where the sorbent was made from peat and Fe by-products. Up-flow columns filled with the prepared sorbent were used to treat water contaminated with As, Cu, Cr, and Zn. Peat effectively adsorbed Cr, Cu, and Zn, whereas approximately 50% of inlet As was detected in the eluent. Iron-sand was effective only for adsorbing As, but Cr, Cu, and Zn were poorly adsorbed. Only iron-peat showed the simultaneous removal of all tested metal (loid)s. Metal (loid) leaching from the spent sorbent at reducing conditions as means to assess the behaviour of the spent sorbent if landfilled was also evaluated. For this purpose, a standardised batch leaching test and leaching experiment at reducing conditions were conducted using the spent sorbent. It was found that oxidising conditions, which prevailed during the standardised batch leaching test, could have led to an underestimation of redox-sensitive As leaching. Substantially higher amounts of As were leached out from the spent sorbents at reducing atmosphere compared with oxidising one. Furthermore, reducing environment caused As(V) to be reduced into the more-toxic As (III).

Leaching of metal(loid)s from ashes of spent sorbent and stabilisation effect of calcium-rich additives

“…Based on the contaminant concentrations detected in the leachate, the waste can be deposited at landfills for (i) inert, (ii) non-hazardous or (iii) hazardous wastes. In previous studies (Kasiuliene et al 2019a , b ), it was concluded that the spent peat and iron–peat could not be landfilled at landfills for hazardous waste. The leaching of As, which intensified drastically under the reducing conditions, was one of the main factors hindering the landfilling.…”

“…To tackle these issues, we combined two highly efficient sorbents, namely peat and Fe oxide, into one sorbent (iron–peat) that can simultaneously remove cationic (Cu, Zn) and anionic (As (arsenate, arsenite), Cr (chromate, dichromate)) contaminants from contaminated water (Kasiuliene et al 2018 ; Kasiuliene et al 2019a ). Thus, the amount of the resulting spent sorbent is lower in comparison with the case where several sorbents are used.…”

“…The necessity of coating peat with Fe oxides in order to achieve the simultaneous removal of several contaminants was confirmed using only non-coated peat or only Fe oxides (coated on sand), in which case each was effective only for certain elements, but not for all of the investigated elements (As, Cr, Cu and Zn) simultaneously. The efficiency of the iron–peat was attributed to the increased Fe content, larger specific surface area and the presence of organic matter (Kasiuliene et al 2019a ).…”

“…It was also determined that about one-third of the As(IV) was reduced to As(III). Although the leaching of Cu and Zn was less affected by the reducing environment, there was an indication that from the long-term perspective, elevated concentrations of these metals could be expected in the landfill leachate along with As (Kasiuliene et al 2019a ).…”

Reduction of Lead and Antimony Ions from the Crystal Glass Wastewaters Utilising Adsorption

“…Peat also has a lot of functional groups, such as carboxyl, phenolic, hydroxyl, etc. (Figure 2a), which contributed significantly to the interactions with the positively charged heavy metal ions, and, consecutively, to its high adsorption capability [15,25,30]. Thus, the removal mechanism of peat is based upon metal biosorption, including chemisorption, complexation, adsorption on the surface, diffusion through pores, and ion exchange.…”