Amine contaminants removal using alginate clay hybrid composites and its effect on foaming

International Journal of Industrial Chemistry https://doi.org/10.1007/s40090-019-0180-9 RESEARCH Amine contaminants removal using alginate clay hybrid composites and its effect on foaming Anjali Achazhiyath Edathil1 · Priyabrata Pal1 · Fawzi Banat1 Received: 2 July 2018 / Accepted: 14 March 2019 © The Author(s) 2019 Abstract Heat stable salts such as total organic acids (TOA) and heavy metals are well known contaminants in the acid gas removal systems operating using alkanolamines such as methyldiethanolamine (MDEA, 50 wt%). Decontamination of TOA and heavy metals from lean MDEA always remain as a challenge to the gas industry, as accumulation of TOA deteriorates the solvent quality, weakens the absorption capacity and enhances foaming problems leading to huge loss of MDEA and presence of heavy metals results in corrosion and fouling of equipment. Equilibrium batch adsorption were carried out using calcium alginate clay hybrid composites (CAH) containing sepiolite and bentonite for assessing the sorption performance of TOA and heavy metals such as chromium and iron from industrial lean MDEA solutions. The physiochemical properties of the adsorbent were elucidated using SEM, EDX and FTIR analysis. The effects of operational parameters such as amount of sorbent, contact time and temperature on the sorption capacity were also investigated. Kinetics results indicated that the chemisorption nature. The pseudo-second order model gave the best fit. The adsorption efficiency increased with increasing the temperature. Adsorption followed type VI isotherm according to the IUPAC classification, with sorption taking place in different stages. Regeneration studies revealed that 4% CaCl2 acts as an effective eluting agent and no reduction in capacity was observed even after 3 cycles of regeneration. Foaming studies carried out with treated lean MDEA confirmed the reduction in foam of MDEA solutions owing to the effective removal of foam creators such as TOA from lean MDEA by CAH composites. A 15.8% reduction in TOA content was found to decrease the foam height by 37.5%. Thus, CAH composites containing bentonite and sepiolite are having the potential to reclaim industrial lean MDEA solutions. Keywords Alginate · Clay composites · Adsorption · Lean amine · Foaming Introduction Amine systems employing alkanolamines such as methyldiethanolamine (MDEA) for acid gas absorption are fronting continuous challenge for maintaining and increasing the process throughput and profit. However, the presence of contaminants such as heat stable salts (HSS) and heavy metal Electronic supplementary material The online version of this article (https://doi.org/10.1007/s40090-019-0180-9) contains supplementary material, which is available to authorized users. * Priyabrata Pal * Fawzi Banat 1 Department of Chemical Engineering, Khalifa University, P.O. Box 127788, Abu Dhabi, United Arab Emirates ions hinders the smooth operation and causes system downtime and upsets [1]. These HSS are formed by the interaction of MDEA with acid gases (H2S and CO2), followed with reaction of the formed protonated MDEA (MDEAH+) with strong acid anionic species such as formate, acetate, propionate, thiosulfate etc. and cannot be regenerated by the application of heat [2]. The accumulation of HSS in the amine deteriorates the solvent quality, reduces the H 2S absorption capacity and augments the foaming leading to significant loss of MDEA [3, 4]. On the other hand, metal contaminants produced from the makeup water or due to the corrosion or erosion caused during the continuous running of the plant results in the fouling of the equipment. Therefore, amine reclamation by reducing these impurities to lower levels have become a necessary step that the gas industry needs to be employed for dramatically improving the operation. 13 Vol.:(0123456789) International Journal of Industrial Chemistry Few attempts are reported in literature for the removal of HSS degradation product and heavy metal ions from contaminated amine solutions utilizing services of neutralization [5], vacuum distillation [6], electro dialysis [7–9], ionexchange [10, 11], and adsorption [12–14]. Among these, adsorption using solid sorbents have drawn significant interest owing to their high removal efficiency, ability to remove even traces of contaminants and low operation, installation and regeneration cost. Recently, researchers have intensified their investigations with quest for identifying relatively low cost and biodegradable materials with high sorption capacities, so called the green sorbents for contaminant removal from industrial lean amine [15, 16]. This growing demand has paved the way for utilizing alginate, a widely available polysaccharide harvested from marine brown algae [17] as the starting material for making environmentally benign adsorbents [18–20]. Alginates have the ability to form hydrogels, which can hold large amount of water on crosslinking with metal ions. These hydrogel are three-dimensional networks consisting of carboxylic (–COOH) and hydroxyl (–OH) groups, which facilitate the simultaneous removal of heavy metals and total organic acids from industrial lean MDEA (LA) solutions through ion exchange and electrostatic interaction respectively. However, both gel and dry form of the alginate has limitations such as low mechanical strength and swelling problems, respectively and thus causing operational difficulties [21]. Researchers have recently conceptualized the idea of combining relatively low cost clay materials with environmentally friendly alginate for yielding a new class of hybrid materials called bio composites, and thus, curtailing the congenital problems accompanying the alginate sorbents. The effective composite material developed by incorporating alginate into the network of layered silicates belonging to the smectite family such as montmorillonites, bentonite and microfibrous clays such as sepiolite was reported to have the highest sorption capability for the simultaneous removal of TOA and heavy metals from industrial lean amine solutions [22]. Recent studies reported by Alhseinat et al. [23], confirmed the significant effect of various organic acids on the foaming behavior. However, no studies are reported pertaining to understanding the effect of adsorptive removal of total organic acid (TOA) from lean MDEA solutions and its impact on lessening the foaming problems faced in gas sweetening units using alkanolamines. Moreover, the removal of heavy metals such as chromium and iron are also important for preventing the corrosion of the sweetening units. This work aims to evaluate the potentiality of the contaminant (TOA anions and heavy metal ions) removal from industrial lean MDEA solutions by adsorption using alginate clay composites containing bentonite (CAB) and sepiolite 13 (CAS) and understand its effect on amine foaming. To the best of authors’ knowledge, there are no reported literature that address (...truncated)