Abstract
Natural biopolymers are gaining increasing attention due to their extraordinary affinity towards adsorption of heavy metal ions. In this research, biopolymers such as chitosan and alginate were used to remove contaminants from lean alkanolamine (methyldiethnolamine; MDEA) solvent. The sweetening of natural gas is mostly done by absorption using single or mixed alkanolamine solutions. Alkanolamine solvent quality deteriorates abruptly while absorbing H2S/CO2 from natural gas and causes foaming in natural gas sweetening unit. Different types of organic as well as inorganic species are present as contaminant in lean MDEA solvent. Heat stable salts such as acetate and propionate are present in high amount in lean MDEA solutions and detected using Ion chromatograph and UV-VIS spectrophotometer. Substantial amount of elements (chromium, iron etc.) were detected using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) analysis. Chitosan coated sand (CCS) and calcium alginate (Ca-Alg) beads were prepared and used in batch adsorption studies to monitor the removal of these contaminants in MDEA solvents. FTIR studies and SEM analysis were done to observe the underlying principle of bio-adsorbent preparation. It was observed that both CCS and Ca-Alg removed heavy metal ions like chromium (40% and 61%) and iron (21% and 62%) significantly. Ca-Alg could also remove organic acid anions (36%) appreciably. The maximum uptake capacity for chitosan coated sand was found to be 59.88 μgm/gm for iron and 38.022 μgm/gm for chromium.
Highlights
Natural biopolymers such as chitosan and alginate are gaining momentum due to their extraordinary affinity towards adsorption of heavy metal ions
The novelty of this research work lies in the preparation of chitosan coated sand (CCS) and calcium alginate beads which were used as an adsorbent for the removal of heavy metal ions and organic acid anions accumulated in lean MDEA solution in gas sweetening process
Biopolymers like chitosan and alginates were successful used as adsorbent for the removal of metal ions as well as organic acid anions present in industrial lean MDEA samples obtained from Gasco, Habshan (Abu Dhabi)
Summary
Natural biopolymers such as chitosan and alginate are gaining momentum due to their extraordinary affinity towards adsorption of heavy metal ions. The novelty of this research work lies in the preparation of chitosan coated sand (CCS) and calcium alginate (ca-Alg) beads which were used as an adsorbent for the removal of heavy metal ions (mostly chromium and iron) and organic acid anions accumulated in lean MDEA solution in gas sweetening process. Preparation of sand coated with chitosan and calcium alginate beads used as adsorbents Sand was collected from the campus area of the Petroleum Institute, Abu Dhabi, washed with distilled water and dried. The batch adsorption experiments were conducted using mixed batch reactor technique for % removal of metal ions and organic acid anions using chitosan coated sand (CCS) and calcium alginate (CaAlg) beads. C0 and Cf are the respective ion concentrations in solution initially and at equilibrium after 24 hours
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