For the first time, guar gum-g-(acrylic acid-co-acrylamide-co-3-acrylamido propanoic acid) (GGAAAMAPA), a smart environment-friendly and sustainable interpenetrating polymer network hydrogel having unprecedented thermomechanical/physicochemical properties and excellent recyclability, has been synthesized by the grafting of guar gum (GG) and in situ adjunct allocation of 3-acrylamido propanoic acid (APA) during solution polymerization of acrylic acid (AA) and acrylamide (AM), using N,N′-methylenebisacrylamide (MBA) and potassium persulfate (PPS)–sodium bisulfite (SBS) as a crosslinker and a redox pair of initiators, respectively, through systematic multistage optimization of the constituents and the temperature of the reaction, for a comprehensive understanding of the individual/synergistic superadsorption mechanism during recycling of hazardous dyes, like 2,8-dimethyl-3,7-diamino-phenazine (i.e. safranine, SF), 3,7-bis(dimethylamino)-phenothiazin-5-ium chloride (i.e. methylene blue, MB) and sodium 4{[4(dimethylamino)phenyl]diazenyl}benzene-1-sulfonate (i.e. methyl orange, MO), along with the adsorptive exclusion of metal ions, i.e. M(II), like Pb(II), Cd(II) and Cu(II). The unambiguous in situ addition of APA, the grafting of GG into the AA-co-AM-co-APA (AAAMAPA) matrix and the superadsorption mechanism have been systematically determined by extensive analyses of FTIR, ¹H-/¹³C-NMR, O 1s-/N 1s-/C 1s-/Pb 4f_7/2,5/2-/Cd 3d_5/2,3/2- and Cu 2p_3/2,1/2-XPS, TGA, DSC, XRD, FESEM, EDX, and storage/loss moduli and supported by computational measurements via density functional theory (DFT), along with the measurements of %gel content (%GC), pH at point of zero charge (pH_PZC), %graft ratio (%GR) and network parameters of hydrogels. The prevalence of ionic (I) and variegated interactions, like monodentate (M), bidentate bridging (BB) and bidentate chelating (BC), between GGAAAMAPA and M(II), has also been rationalized by FTIR and fitting of kinetics data to the pseudosecond order model and by the measurement of activation energies of adsorption. The individual/interactive effects of cationic and/or anionic dyes have been rationally determined via extensive UV-Vis analyses at 1 : 1, 1 : 2 and 2 : 1 mole ratios of dyes and pH_i = 2/9, interpreted through the appearance of the metachromic effect, dye-aggregates, π–π stacking interaction, diprotonated MO etc. The BET and Langmuir isotherms have fitted the best to MB and SF/Cd(II)/Cu(II)/Pb(II), respectively. Thermodynamically spontaneous chemisorption processes have shown the maximum adsorption capacities (ACs) of 27.06, 39.35, 40.55, 39.42, and 41.98 mg g⁻¹ for MB, SF, Cd(II), Cu(II) and Pb(II), respectively, at 303 K, adsorbent dose = 0.025 g and initial concentration of dyes/M(II) = 30 ppm.

Herein, gum ghatti-g-(N-isopropylacrylamide-co-3-(N-isopropylacrylamido) propanoic acid-co-sodium acrylate) (GTINIAMSA), a novel interpenetrating terpolymer network hydrogel with unprecedented thermomechanical and physicochemical properties and excellent recyclability, was synthesized via the grafting of gum ghatti (GTI) and the in situ strategic protrusion of 3-(N-isopropylacrylamido) propanoic acid (NIPAMPA) during the solution polymerization of sodium acrylate (SA) and N-isopropylacrylamide (NIPAm) using N,N′-methylenebisacrylamide (MBA) and potassium persulfate (PPS)/sodium bisulfite (SBS) as a cross-linker and redox pair of initiators, respectively, through the systematic multistage optimization of the constituents and the reaction temperature for a comprehensive understanding of the superadsorption mechanism of hazardous metal ions, i.e. M(II/III), like Cd(II), Pb(II), Bi(III) and Sb(III). The unorthodox in situ attachment of NIPAMPA, grafting of GTI into NIPAm-co-NIPAMPA-co-SA (NIAMSA) matrix and the superadsorption mechanism were systematically investigated via extensive unloaded and/or loaded microstructural analyses by FTIR, ¹H-/¹³C-NMR, C 1s-/O 1s-/Cd 3d_5/2,3/2-/Pb 4f_7/2,5/2-/Bi 4f_7/2,5/2-/Sb 3d_3/2-XPS, TGA, XRD, FESEM and EDX, along with the measurements of the %gel content (% GC), pH at point of zero charge (pH_PZC), % graft ratio (% GR) and network parameters of the hydrogels. The prevalence of ionic (I) and variegated coordinative interactions, such as monodentate (M), bidentate bridging (BB) and bidentate chelation (BC), between GTINIAMSA and M(II/III) were also investigated by FTIR and the fitting of kinetics data to a pseudo-second-order model as well as by the measurements of the activation energies of adsorption. The equilibrium adsorption data of M(II/III) were fitted excellently to the Langmuir isotherm model. The thermodynamically spontaneous chemisorption processes showed the excellent maximum adsorption capacities (ACs) of 1477.83, 1568.81, 1582.38 and 1518.09 mg g⁻¹ for Cd(II), Pb(II), Bi(III), and Sb(III), respectively, at 303 K with an adsorbent dose of 0.02 g and initial concentration of M(II/III) = 500–800 ppm.

For the fulfilment of increasing global demand and associated challenges related to the supply of clean-and-safe water, PV has been considered as one of the most attractive and promising areas in desalinating salty-water of varied salinities. In pervaporative desalination, the sustainability, endurance, and structural features of membrane, along with operating parameters, play the dominant roles and impart paramount impact in governing the overall PV efficiency. Indeed, polymeric- and organic-membranes suffer from several drawbacks, including inferior structural stability and durability, whereas the fabrication of purely inorganic membranes is complicated and costly. Therefore, recent development on the high-performance and cost-friendly PV membrane is mostly concentrated on synthesizing composite- and NCP-membranes possessing the advantages of both organic- and inorganic-membranes. This review reflects the insights into the physicochemical properties and fabrication approaches of different classes of PV membranes, especially composite- and NCP-membranes. The mass transport mechanisms interrelated to the specialized structural features have been discussed. Additionally, the performance potential and application prospects of these membranes in a wide spectrum of desalination and wastewater treatment have been elaborated. Finally, the challenges and future perspectives have been identified in developing and scaling up different high-performance membranes suitable for broader commercial applications.