Optimization of Carbon Dioxide and Valeric Acid Utilization for Polyhydroxyalkanoates Synthesis by Cupriavidus necator

The utilization of captured CO₂ as a part of the CO₂ capture and storage system to produce biopolymers could address current environmental issues such as global warming and depletion of resources. In this study, the effect of feeding strategies of CO₂ and valeric acid on cell growth and synthesis of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] in Cupriavidus necator was investigated to determine the optimal conditions for microbial growth and biopolymer accumulation. Among the studied CO₂ concentrations (1–20 %), microbial growth and poly(3-hydroxybutyrate) accumulation were optimal at 1 % CO₂ using a gas mixture at H₂:O₂:N₂ = 7:1:91 % (v/v). When valeric acid was fed together with 1 % CO₂, (R)-3-hydroxyvalerate synthesis increased with increasing valeric acid concentration up to 0.1 %, but (R)-3-hydroxybutyrate synthesis was inhibited at >0.05 % valeric acid. Sequential addition of valeric acid (0.05 % at Day 0 followed by 0.025 % at Day 2) showed an increase in 3HV fraction without inhibitory effects on 3HB synthesis during 4 d accumulation period. The resulting P(3HB-co-3HV) with 17–32 mol  % of 3HV is likely to be biocompatible. The optimal concentrations and feeding strategies of CO₂ and valeric acid determined in this study for microbial P(3HB-co-3HV) synthesis can be used to produce biocompatible P(3HB-co-3HV).     

Microbial degradation of poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) in compost

The microbial degradation of tensile test pieces made of poly(3-hydroxybutyrate) [P(3HB)] or copolymers with 10% [P(3HB-co-10%3HV)] and 20% [P(3HB-co-20%3HV)] 3-hydroxyvaleric acid was studied in small household compost heaps. Degradation was measured through loss of weight (surface erosion) and changes in molecular weight and mechanical strength. It was concluded, on the basis of weight loss and loss of mechanical properties, that P(3HB) and P(3HB-co-3HV) plastics were degraded in compost by the action of microorganisms. No decrease inM _w could be detected during the degradation process. The P(3HB-co-20%3HV) copolymer was degraded much faster than the homopolymer and P(3HB-co-10%3HV). One hundred nine microbial strains capable of degrading the polymersin vitro were isolated from the samples used in the biodegradation studies, as well as from two other composts, and identified. They consisted of 61 Gram-negative bacteria (e.g.,Acidovorax facilis), 10 Gram-positive bacteria (mainlyBacillus megaterium), 35Streptomyces strains, and 3 molds.     

Accumulation of Polyhydroxyalkanoates by Rhizobacteria Underneath Nickel-Hyperaccumulators from Serpentine Ecosystem

Nickel-resistant bacteria isolated from underneath Ni-hyperaccumulators growing on serpentine soils were screened for production of polyhydroxyalkanoates. These rhizobacteria accumulated poly-3-hydroxybutyric acid [P(3HB)] accounting 3.9–67.7% of cell dry weight during growth in gluconate and/or glucose. Cupriavidus pauculus KPS 201 utilized only gluconate and accumulated about 67.7% P(3HB) while, Bacillus firmus AND 408 utilized both carbon sources for polymer synthesis. The isolates being resistant to Ni also accumulated substantial amount of P(3HB) when grown in presence of the heavy metal and this was revealed by transmission electron microscopic studies. Although B. firmus AND 408 produced only P(3HB) at higher concentrations of gluconate, C. pauculus KPS 201 synthesized copolymer of 3-hydroxybutyric acid (3HB) and 3-hydroxyvaleric acid (3HV) [P(3HB-co-3HV)]. In presence of 0.8% gluconate and 4 mM Ni, KPS 201 cells produced PHA amounting 81% CDW, which contained 76 and 24 mol% 3HB and 3HV monomers, respectively.     

Degradation of Poly(3-hydroxybutyrate) and Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) by Some Soil Aspergillus spp.

Systematic screening of 45 soil fungi for degradation polyhydroxyalkanoic acids (PHAs) has led to the selection of 6 potent Aspergillus isolates belonging to A. flavus, A. oryzae, A. parasiticus, and A. racemosus. Degradation of PHAs as determined by tube assay method revealed that these Aspergillus spp. were more efficient in degrading poly(3-hydroxybutyrate) [P(3HB)] compared to copolymer of 3-hydroxybutyric acid and 3-hydroxyvaleric acid (P3HB-co-16% 3HV). Moreover, the extent of degradation in mineral base medium was much better than those in complex organic medium. For all the Aspergillus spp. tested, maximum degradation was recorded at a temperature of 37°C with significant inhibition of growth. The optimum pH range for degradation was 6.5–7.0 with degradation being maximum at pH 6.8. The extent of polymer degradation increased with increase in substrate concentration, the optimum concentration for most of the cultures being 0.4% and 0.2% (w/v) for P(3HB) and P(3HB-co-16%3HV) respectively. Supplementation of the degradation medium with additional carbon sources exerted significant inhibitory effect on both P(3HB) and P(3HB-co-16%3HV) degradation.     

Production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) from various carbon sources by batch-fed cultures ofAlcaligenes eutrophus

Copolyesters of 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV) were produced at 30°C from various carbon sources byAlcaligenes eutrophus under batch-fed growth conditions. The production of P(3HB-co-3HV) from butyric and pentanoic acids was effective under nitrogenlimited conditions, and the conversion of carbon sources into copolyester was as high as 56 wt% at a C/N molar ratio of 40. In contrast, under excess-nitrogen conditions (C/N<10), cell growth was good, while P(3HB-co-3HV) production was partially inhibited. The production of P(3HB-co-3HV) from fructose and propionic acid was almost completely inhibited under excess-nitrogen conditions.     

Polymers,the Light at the End of Dark Fermentation: Production of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) by a Photoheterotrophic Consortium

Journal of Polymers and the Environment - In this study, the photoheterotrophic consortium C4 was used to produce the copolymer [P(3HB-co-3HV)]. PHA production was enhanced by using response...     

Increased 3HV Concentration in the Bacterial Production of 3-Hydroxybutyrate (3HB) and 3-Hydroxyvalerate (3HV) Copolymer with Acid-Digested Rice Straw Waste

Bacterial synthesis of 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV) copolymer [P(3HB-co-3HV)] using the hydrolysate of rice straw waste as a carbon source was affected by the composition of the hydrolysate, which depends highly on the rice straw pretreatment condition. Acid digestion with 2 % sulfuric acid generated larger production of P(3HB-co-3HV) than 6 % sulfuric acid, but 3HV concentration in the copolymer produced with 2 % acid hydrolysate was only 8.8 % compared to 18.1 % with 6 % acid hydrolysate. To obtain a higher 3HV mole fraction for enhanced flexibility of the copolymer, an additional heating was conducted with the 2 % acid hydrolysate after removal of residual rice straw. As the additional heating time increased a higher concentration of levulinic acid was generated, and consequently, the mole fraction of 3HV in P(3HB-co-3HV) increased. Among the conditions tested (i.e., 20-, 40-, 60-min), 60-min additional heating following 2 % sulfuric acid digestion achieved the highest 3HV mole fraction of 22.9 %. However, a longer heating time decreased the P(3HB-co-3HV) productivity, probably due to the increased intermediates concentrations acting as inhibitors in the hydrolysates. Therefore, the use of additional heating needs to consider both the increase in the 3HV mole fraction and the decrease in the P(3HB-co-3HV) productivity.     

Stability of Aqueous Suspensions of Medium-Chain-Length Poly-3-Hydroxyalkanoate Particles

Although poly-3-hydroxyalkanoates (PHAs) and particularily medium-chain-length (mcl)-PHAs are likely to find industrial applications in a latex form, very few studies have examined their behavior in aqueous suspension and none have examined the dense suspensions required commercially. For this reason, the stability of mcl-PHA latexes containing saturated aliphatic (65 mol% 3-hydroxynonanoate, PHN), and for the first time, with vinyl (PHNU) or carboxylated side chains was examined. At 4 g L^?1 with no stabilizing agent, PHNU nanoparticles (199.4 ± 3.6 nm) were significantly smaller than those of PHN (211.5 ± 6.4 nm) while carboxylated PHN nanoparticles (76.1 ± 6.4 nm) were substantially smaller than those of either PHN or PHNU with particles stable for more than 110 days. Increasing the PHN concentration to 10 g L^?1 also resulted in stable latexes but with larger particles (410.8 ± 5.2 nm). Adjusting the pH of the suspending medium (water) before addition of the polymer (dissolved in acetone) resulted in much smaller PHN particles at pH = 11.3 (134 ± 2 nm) than at pH = 4.3 (312 ± 8 nm) at a 4 g L^?1 final polymer concentration. Zeta potentials of PHN suspensions decreased with pH, likely due to the carboxyl end groups. Above a pH of 4.0, adjusting the pH after particle formation had little effect. NaCl addition could be used to agglomerate and ultimately precipitate the particles. Stabilizers such as surfactants will likely be required to produce denser mcl-PHA latexes with suitable particle size for certain applications such as coatings and toner production.     

Melt Compounded Blends of Short and Medium Chain-Length Poly-3-hydroxyalkanoates

Blends of poly-3-hydroxybutyrate with an elastomeric medium-chain-length poly-3-hydroxyalkanoate (MCL-PHA), containing 98 mol% 3-hydroxyoctanoate and 2 mol% 3-hydroxyhexanoate (referred to as PHO), were prepared by melt compounding. Coarsening of the droplet-matrix morphology of the blends was noted as the PHO content increased beyond 5 wt%; this was attributed to the significant viscosity mismatch between the components. Addition of PHO improved the thermal stability of the blends, reduced their crystallinity and resulted in shifts in their melting and crystallization temperatures. The blends had improved tensile strain at break. The unnotched impact strength showed a threefold increase at 30 wt% PHO content. Cross-linking of PHO using a peroxide initiator increased its viscosity, thus improving the morphology and mechanical properties of the blends.     

Accumulation of poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid-co-4-hydroxyvaleric acid) by mutants and recombinant strains ofAlcaligenes eutrophus

Alcaligenes eutrophus accumulated a terpolyester of 3-hydroxybutyric acid (3HB), 3-hydroxyvaleric acid (3HV), and 4-hydroxyvaleric acid (4HV) during cultivation with 4HV as carbon and energy source under nitrogen starvation. The polyester accumulated by wild-type strains under these conditions contained 4HV at a molar fraction of approximately 5 mol% only. A catabolic pathway of 4HV was postulated, which included the activation of 4HV to 4HV-CoA and a conversion of 4HV-CoA to 3HV-CoA. Tn5::mob-induced mutants were isolated fromA. eutrophus HF39, which were affected in 4HV and/or valeric acid catabolism. Among 83 mutants were 27 4HV-negative or 4HV-leaky mutants; two mutants were identified which accumulated a terpolyester with a molar fraction of 10.1 to 22.7 mol% 4HV. In addition, a further increase in the molar fraction of 4HV in poly(3HB-co-3HV-co-4HV) and a two- to fourfold increase in the PHA synthase activity were monitored in these mutants or others and also in HF39, if the cells were complemented with the hybrid plasmid pHP1014::PP1, which contained the PHA biosynthesis genes ofA. eutrophus H16. Application of mutagenesis plus recombinant DNA techniques resulted in the accumulation of a terpolyester with up to 30 mol% 4HV and with approximately equimolar fractions of 3HB, 3HV, and 4HV.     

Determination of nitrous oxide, methane, and ammonia emissions from a swine waste composting process

The amounts of harmful gas emissions from the process of composting swine waste were determined using an experimental composting apparatus. Forced aeration (19.2–96.1 l/m³/min) was carried out continuously, and exhaust gases were collected and analyzed periodically. With weekly turning and the addition of a bulking agent in order to decrease the moisture content and increase air permeability, the temperature of most of the contents rose to 70°C and composting was complete within 3–5 weeks. NH₃, CH₄, and N₂O emissions were high in the early stage of composting. About 10%–25% of the nitrogen in the raw material was lost as NH₃ gas during composting. The emission rate of NH₃ mainly depended on the aeration rate, so that as the aeration rate rose, the level of NH₃ emissions increased. The CH₄ and N₂O emissions could be kept lower with adequate treatment at more than 40 l/m³/min aeration. N₂O may be mainly the result of the denitrification of NO _x -N in the additional matured compost used as a composting accelerator. Received: September 11, 1998 / Accepted: November 8, 1999     

Influence of aeration on CH4, N2O and NH3 emissions during aerobic composting of a chicken manure and high C/N waste mixture

Co-composting of chicken manure, straw and dry grasses was investigated in a forced aeration system to estimate the effect of aeration rates on NH₃, CH₄ and N₂O emissions and compost quality. Continuous measurements of gas emissions were carried out and detailed gas emission patterns were obtained using an intermittent-aeration of 30 min on/30 min off at rates of 0.01 (A1), 0.1 (A2) and 0.2 (A3) m³ min⁻¹ m⁻³. Concentrations of CH₄ and N₂O at the low aeration rate (A1) were significantly greater than those at the other two rates, but there was no significant difference between the A2 and A3 treatments. CH₄ and N₂O emissions for this mixture could be controlled when the composting process was aerobic and ammonia emissions were reduced at a lower aeration rate. Comparison of CH₄, N₂O, NH₃ emissions and compost quality showed that the aeration rate of the A2 treatment was superior to the other two aeration rates.     

Biodegradation of pretreated polyethylene film by Pseudomonas aeruginosa AMB-CD-1

A comparative study evaluated the acid, alkali, and heat-treated polyethylene biodegradation efficiency of Pseudomonas aeruginosa AMB-CD-1. The polyethylene (PE) pieces were separately treated with heat (50°C), acid (1N HCl), and alkali (1N NaOH) and then washed with water before use. All the treated samples were analyzed through thermogravimetric analysis. In addition, weight and temperature changes during the decomposition reactions were also measured and determined. In these treatments, the PE films of heat-treated and acid-treated low-density polyethylene (LDPE) indicated more significant weight loss at 120°C (48.99% and 40.75%, respectively) as compared to their control or untreated PE and alkali-treated LDPE (21.84% and 24.68%, respectively). A biodegradation assay was then conducted with treated and untreated LDPE films with P. aeruginosa AMB-CD-1 strain. Fourier transform infrared spectroscopy analysis revealed that the heat or acid-pretreated samples with isolate AMB-CD-1 displayed peaks at 2922.84, 2923.97, and 1450.31, 874.22 cm⁻¹ for C–H stretching deformation vibration, CH₂ scissoring vibration, –CHO stretching, and strong alkyl structure, respectively. Furthermore, the new peaks with a significant difference at 2500–2000 cm⁻¹ (O═C═O, O–H stretching vibration: carboxylic acid) and 1500–1000 cm⁻¹ (–CHO and C═O stretching) were noticed in the infrared spectral range of LDPE degradation. Modifications in the functional group provided evidence that biodegradation had impacted the chemical structure of the LDPE film. Additionally, it was demonstrated that pretreating LDPE films with heat or acid could speed up their biodegradation.     

Styrene/Lignin-Based Polymeric Composites Obtained Through a Sequential Mass-Suspension Polymerization Process

A modified sequential mass-suspension polymerization was employed to ensure adequate dispersion of lignin into the monomeric phase. Due to its complex macromolecular structure and low compatibility with styrene, eucalyptus wood-extracted lignin, via a modified Kraft method, was esterified with methacrylic anhydride to ensure organic phase homogeneity into the reaction medium. Infrared spectroscopy showed a decrease in the hydroxyl band, a characteristic of natural lignin (3200–3400 cm^?1) and an increase in the characteristic ester band (1720–1740 cm^?1) whereas nuclear magnetic resonance measurements exhibited intense peaks in the range from 1.7 to 2.05 ppm (–CH₃) and 5.4 to 6.2 ppm (=CH₂), related to methacrylic anhydride. Comparatively, the esterified lignin also displayed an increase of its glass transition temperature for 98?°C, related to natural lignin, whose T _g was determined to be equal to 91?°C. Styrene/lignin-based polymers exhibited higher average molar masses in comparison to the values observed for polystyrene synthesized with similar amounts of benzoyl peroxide, due to the ability of lignin to act as a free-radical scavenger. Composites obtained with styrene and natural or esterified lignin were successfully synthesized, presenting regular morphology and proper lignin dispersion. Based on a very simple polymerization system, it is possible to enhance the final properties of polystyrene through the incorporation of lignin, which represents an important platform for developing attractive polymeric materials from renewable resources.     

Municipal Wastes Treatment and Production of Polyhydroxyalkanoate by Modified Two-Stage Batch Reactor

The municipal wastes were utilized as substrate for polyhydroxyalkanoate (PHA) using two strains of Bacillus licheniformis (PHAs-007, wild type and M2-12, mutant). Municipal wastes were subjected to separate wastewater and biosolid. Municipal biosolid was digested by anaerobic bacteria thereafter only the supernatant with soluble organic compounds was subjected into the PHA-producing reactor containing municipal wastewater. The mutant strain M2-12 gave the highest value of biomass (42.0 ± 2.0 g/L) and PHA concentration (37.4 ± 1.0 g/L with 88.9 % of dry cell weight, DCW) and reduced 76.5 % of soluble chemical oxygen demand after 60 h of cultivation. The value of pH, biochemical oxygen demand and total solid of the reclaimed wastewater after PHA recovery was 7.1, 20 and 97 mg/L, respectively. Moreover, the polymers produced by both strains of B. licheniformis were characterized. The resultant polymer from B. licheniformis PHAs-007 and M2-12 cultivated in the PHA-producing reactor was identified as poly-3-hydroxybutyrate-co-3-hydroxyvalerate [P(3HB-co-3HV)] and poly-3-hydroxybutyrate-co-4-hydroxybutyrate [P(3HB-co-4HB)], respectively. The results suggesting that the production of PHA by municipal wastes is feasible thus the PHA production stage can be integrated in waste treatment to produce PHA and treated municipal wastes at the same time.     

Biodegradation characteristics of organic matters in swine carcasses under different initial operating conditions of simulated anaerobic lysimeter

This study was aimed to investigate the biodegradation characteristics of organic matters in swine carcasses. The lysimeters were simulated with different initial operating conditions: 30 % volumetric moisture content and no sludge addition for lysimeter A (control), 30 % volumetric moisture content and anaerobic sludge addition for lysimeter B, and 40 % volumetric moisture content and anaerobic sludge addition for lysimeter C. The degradation efficiency (18.4 %) of lysimeter B was higher than that (15.2 %) of lysimeter A due to anaerobic sludge addition. Lysimeter B showed higher CH₄ yield (15.6 L/kg VS) and CH₄ production rate (0.41 L/kg VS days) compared to lysimeter A by 31 % and 14 %, respectively. In addition, the degradation efficiency improved from 18.4 % (lysimeter B) to 26.3 % (lysimeter C) by increasing volumetric moisture content. The CH₄ yield (22.9 L/kg VS) and CH₄ production rate (0.68 L/kg VS days) of lysimeter C were higher than those of lysimeter B, respectively. Total organic carbon (TOC) removed in lysimeter C was converted to leachate (20.3 %) and gas (6.0 %), whose values were higher than those of lysimeter A and B. These results demonstrated that the proper control of initial operating conditions could accelerate the anaerobic degradation of organic matters in swine carcasses.     

Stabilization of sewage sludge in the presence of nanoscale zero-valent iron (nZVI): abatement of odor and improvement of biogas production

The potential benefits of nanoscale zero-valent iron (nZVI) on sludge stabilization, either the abatement of odor or the improvement of biogas production, were investigated in this study. Two commercial-grade microscale iron powders were also utilized for comparison. Adding 0.10 wt% of nZVI in sludge during anaerobic incubation significantly reduced the concentration of H₂S in biogas by 98.0 % (96.2–98.9 %), probably attributed by reactions between sulfides and the neo-formed hydrous Fe(II)/Fe(III) oxides layer at the surface of ZVI nanoparticles. Meanwhile, the percentage of P in bioavailable fractions decreased from 76.8 to 52.5 %, possibly due to the formation of vivianite [Fe₃(PO₄)₂]. Furthermore, 0.10 wt% of nZVI in anaerobic digestion for 17 days enhanced the concentration of CH₄ in biogas by 5.1–13.2 % and improved the production of biogas and methane by 30.4 and 40.4 %, respectively. The amendment of iron nanoparticles during anaerobic digestion can not only effectively reduce H₂S in biogas, but also potentially boost methane production significantly.     

Cardanol Polymerization Under Acid Conditions By Addition And Condensation Reactions

Cashew nut shell liquid (CNSL) is a byproduct of the cashew nut industry and consists predominantly of phenolic compounds that have an side chain with different degrees of unsaturation. Cardanol, one of these components, is biodegradable and widely available. Studies have revealed several polymerization reactions involving cardanol. However, the mechanisms and detailed structures of polymerization reactions have not been explored, although the final product shows different applications. In this work, we evaluated the mechanism and the products structure of the reaction of cardanol with: (i) boron trifluoride diethyl etherate (BF₃O(CH₂CH₃)₂), and (ii) formaldehyde. The characterizations were performed by FTIR, ¹H NMR, SEC and TGA. The results show that the reaction of cardanol with aldehyde produces the expected like-comb structure with a long hydrocarbon pendent chain. Nevertheless, the reaction of cardanol with BF₃O(CH₂CH₃)₂ can exhibits a more complex structure since it was identified aromatic ring linkages, besides the expected polymerization through C=C.     

Catalytic gasification of tars from a dumping site

The work deals with catalytic gasification, pyrolysis and non-catalytic gasification of tar from an industrial dumping site. All experiments were carried out in a vertical stainless steel gasification reactor at 800 °C. Crushed calcined dolomite was used as the gasification catalyst. Parameters such as addition of water and air, and the influence of the catalyst in regard to the composition of the process gas were investigated. The catalytic gasification experiment in the steady state produced process gas with the composition: 56 % of H₂, 9 % of CO, 11 % of CH₄ and 12 % of CO₂ (mol.%). Concentration of the C₂ fraction was lower than 1 mol.%. Volume flow of air was later changed from 120 to 230 ml min^?1 reducing the amount of hydrogen to 51 mol.% and that of methane to 10 mol.%. Process gas created in a non-catalytic gasification process contained 26–30 mol.% of methane, 13–15 mol.% of carbon monoxide and 15–17 mol.% of the C₂ fraction and lower amounts of hydrogen (20 mol.%) and carbon dioxide (2–3 mol.%). The highest apparent conversion of tar was reached in the catalytic gasification processes. A higher rate of catalyst deactivation can be observed when water or air is not added.     

Magnetic Cr(VI) Ion Imprinted Polymer for the Fast Selective Adsorption of Cr(VI) from Aqueous Solution

In this study, a novel magnetic Cr(VI) ion imprinted polymer (Cr(VI)-MIIP) was successfully synthesized and used as a selective sorbent for the adsorption of Cr(VI) ions from aqueous solution. It can be synthesized through the combination of an imprinting polymer and magnetic nanoparticles. The high selectivity achieved using MIIP is due to the specific recognition cavities for Cr(VI) ions created in Cr(VI)-MIIP. Also, the magnetic properties that could be obtained using magnetic nanoparticles, helps to separate adsorbent with an external magnetic field without either additional centrifugation or filtration procedures. The magnetic Fe₃O₄ nanoparticles (MNPs) were synthesized using an improved co-precipitation method and modified with tetraethylorthosilicate (TEOS) before imprinting. The magnetic Cr(VI) ion imprinted polymer was prepared through precipitation copolymerization of 4-vinylpyridine as the complexing monomer, 2-hydroxyethyl methacrylate as a co-monomer, the Cr⁶⁺ anion as a template, and ethylene glycol dimethacrylate (EGDMA) as a cross-linker in the presence of modified magnetite nanoparticles. This novel synthesized sorbent was characterized using different techniques. Batch adsorption experiments were performed to evaluate the adsorption conditions, selectivity, and reusability. The results showed that the maximum adsorption capacity was 39.3 mg g^?1, which was observed at pH 3 and at 25?°C. The equilibrium time was 20 min, and the amount of adsorbent which gave the maximum adsorption capacity was 1.7 g L^?1. Isotherm studies showed that the adsorption equilibrium data were fitted well with the Langmuir adsorption isotherm model and the theoretical maximum adsorption capacity was 44.86 mg g^?1. The selectivity studies indicated that the synthesized sorbent had a high single selectivity sorption for the Cr(VI) ions in the presence of competing ions. Thermodynamic studies revealed that the adsorption process was exothermic (\(\Delta H\)?<?0) and spontaneous (\(\Delta G\)?<?0). In addition, the spent MIIP can be regenerated up to five cycles without a significant decrease in adsorption capacity.