Partition of humic acids using alkaline aqueous two‐phase systems constituted of alcohol and hydroxides

Abstract

BACKGROUNDHumic acids (HAs) are macromolecules classified within the group of humic substances that are mainly related to the agricultural and environmental sectors, but they have attracted interest from the medicine, pharmaceutical, and cosmetic industries. However, these latter sectors depend on developing extraction and purification technologies for adequate use. Thus, this paper aims to study the partitioning and recovery of HA using alkaline two‐phase aqueous systems (ATPSs) based on alkali metal‐based hydroxides and alcohols. Initially, the influence of alcohols (methanol, ethanol, 1‐propanol, and 2‐propanol) and hydroxides (NaOH, KOH, and LiOH) in the phase diagrams construction was addressed.RESULTSThe phase formation is correlated to an increase in the hydrophobicity of alcohols and hydroxides, which allows for the enlargement of the biphasic region. In the proposed systems, HA is always partitioned to the hydroxide‐rich phase. Increasing the hydrophobicity of the alcohol favors the migration of HA to the opposite phase, while increasing the hydrophilicity of the hydroxides leads to better partition and recovery values. It was observed that increasing TLL favors the recovery of HA. Furthermore, there was a decrease in alcohol concentration in the hydroxide‐rich phase with an increase in the alkyl chain and TLL, improving the recovery. Finally, the best reached‐recovery value was 98.18 ± 0.41% (KHA = 0.038 ± 0.02) for ATPS formed by 1‐propanol + NaOH with TLL ≈ 55 at 298 K.CONCLUSIONSThe alkaline systems can be a novel route for recovering humic substances from the environment.This article is protected by copyright. All rights reserved.

Salting-out as a Fast and Simple Method for First-Step Separation of Biobased 1,3-Propanediol

“…In addition, it can be seen that the potassium-based salts showed better K and Y% values, in agreement with the log D values: K 2 HPO 4 (−5.64) > K 3 PO 4 (−5.35) > K 2 CO 3 (−2.67). Ethanol proved to be more efficient at partitioning 1,3-PDO than 2-propanol . It is known that the solubility of alcohols in water depends on the size of their C chains and that it decreases as the number of C increases.…”

“…Ethanol proved to be more efficient at partitioning 1,3-PDO than 2-propanol. 47 It is known that the solubility of alcohols in water depends on the size of their C chains and that it decreases as the number of C increases. Therefore, the salting-out effect caused by the salts had a greater impact on the K and Y% values.…”

“…Ethanol has a lower boiling temperature, which can be separated by applying controlled evaporation, thus leading to the isolation of 1,3-PDO and the recycling and reuse of ethanol, allowing it to be used to create a new extraction system. 47 According to the literature, 56 an ultrafiltration step can isolate glycerol from the salt phase. Furthermore, ultrafiltration is a method that also tends to increase the purity of the target molecule.…”

“…The conceptual process diagram proposed in Figure comprises the steps of 1,3-PDO and glycerol partitioning in the system proposed, target compound isolation from the top (ethanol-rich) and bottom (salt-rich) phases, and the recovery and reuse of the phase-forming components of the salting-out extraction. Ethanol has a lower boiling temperature, which can be separated by applying controlled evaporation, thus leading to the isolation of 1,3-PDO and the recycling and reuse of ethanol, allowing it to be used to create a new extraction system . According to the literature, an ultrafiltration step can isolate glycerol from the salt phase.…”