The increasing production of protein-rich waste, primarily from the household and food industries, associated with the growing global population has imposed a negative environmental burden on society at large. Protein waste is a growing international concern, with more unsegregated waste released from developing countries. This work explored the sorption behavior of amorphous plant extract of Humulus lupulus , towards bovine serum albumin as a representative model protein. The adsorbed proteins analyzed using scanning electron microscopy, revealed irregular beads masking the surface cues and changing the surface smoothness, further validated by atomic force microscopy. The atomic force microscopy analysis showed an increase in the surface potential of pre-adsorbed material (−60.2 mV to 42.5 mV) compared to post-adsorbed complex (−736 mV to 640 mV) suggesting the protein interaction on the plant surface. Differential scanning calorimetry indicated the possible interaction between protein and surface which is responsible for showing a shift in the enthalpy pattern of the surface pre- and post-adsorption. Change in enthalpy pattern, higher surface potential, and shift in Fourier-transform infrared spectroscopy binding pattern indicates an interaction between plant surface and protein that was further validated and confirmed using the adsorption isotherm. The adsorption isotherm towards bovine serum albumin protein followed the Freundlich isotherm with k and n values of 1.143 and 1.157, respectively. The Freundlich isotherm pattern observed for the material has suggested H. lupulus plant extract as a suitable surface for protein adsorption. The study opens the avenue for the adsorption kinetics of different proteins and establishing the plant extract as a suitable remediation solution for environmental sustainability.

In the present study, a more potential and economical method is described to reutilize a waste adsorbent as the waste Cu2+-loaded poly(AAc/AM/SH) SAHs were not undergone any regeneration process and directly applied to adsorb phosphate ion from another waste solution. The SAHs poly(AAc-AM-SH) was anionic in nature, thus show higher affinity toward Cu2+ ions, but it hardly adsorb anions due to its characteristics of negative charge existing on the polymeric surface. The adsorption of Cu2+ makes it positively charged moiety and so it is being capable of anions/anionic dye adsorption. The various factors affecting the phosphate adsorption including pH, contact time, initial concentration of the phosphate were systematically investigated. The maximum phosphate adsorption was obtained 87.62 mg/g. The adsorption data fitted the Langmuir adsorption isotherm. The desorption studies showed that the regeneration of the poly(AAc/AM/SH)–Cu SAHs adsorbent can be easily achieved. The results confirmed that poly (AAc/AM/SH) superabsorbent hydrogels loaded with Cu2+ ion can be applied as effective solid adsorbent for the removal of phosphate ions from waste water and aqueous effluents.

A novel superabsorbent hydrogel (SAH) composed of poly(acrylic acid-sodium acrylate-acrylamide)/sodium humate poly(AAc-SA-AM)/SH was synthesized and applied as adsorbent to adsorb crystal violet (CV) and methylene blue (MB) dye in its dry as well as swollen condition from the aqueous solutions. The swelling ratios of the synthesized SAHs were determined. The factors affecting adsorption capacity of the poly(AAc-SA-AM)/SH hydrogel, such as contact time, temperature, SH content (wt.%), and initial concentration of both dyes, were systematically investigated. The experimental data suggested that an appropriate addition of SH (2.40 wt.%) increases the swelling ratio as well as adsorption capacity of poly(AAc-SA-AM) hydrogel. The adsorption capacity was approximately equal for the dry (231mg/g for CV and 270mg/g for MB) and equilibrium SAHs (240mg/g for CV and 278mg/g for MB). The results also revealed that the swollen SAHs exhibited higher adsorption rate than the dry SAHs due to presence of functional anionic groups in its elongated state. The adsorption equilibrium data fitted very well to the Langmuir isotherm than the Freundlich isotherm. Thermodynamic parameters of adsorption were also calculated, and the negative change in Delta G degrees and Delta H degrees confirmed that the dye adsorption process was spontaneous and exothermic in nature. The kinetic studies showed that the adsorption phenomenon followed the pseudo-second-order kinetic model.

The traditional method for the treatment of used adsorbents is usually recovery for recycling or direct discarding them. In the present study, a more potential and economical method is described to reutilize a waste adsorbent. Poly(AAc/AM/SH) SAHs have proved to be a good adsorbent for cationic MB dye, and after adsorption, the SAHs were recovered for recycling. In this work, the waste MB dye loaded poly(AAc/AM/SH) SAHs were not recovered but directly applied to adsorb an anionic MO dye from another waste solution. The poly(AAc/AM/SH) SAHs after the MB dye adsorption were stable and suitable for MO dye adsorption for altered surface structures within a wide pH range. The various factors affecting the MO dye adsorption, including pH, contact time, ionic strength, initial concentration of the MO dye, and temperature, were systematically investigated. The equilibrium adsorption data fitted very well to the Langmuir adsorption isotherm and the maximum MO dye adsorption capacity reached to a high of 134mg/g at 30 degrees C. The thermodynamic parameters such as Delta H-0, Delta G(0), and Delta S-0 for the MO dye adsorption processes onto the SAHs were also evaluated, and the obtained negative Delta G(0) and Delta H-0 values confirmed that the MO adsorption process was spontaneous as well as exothermic. The kinetic studies indicate that the MO dye adsorption process was well consistent with the pseudo-second-order kinetic model. The desorption studies showed that the regeneration of the poly(AAc/AM/SH)-MB SAHs adsorbent can be easily achieved.

A novel superabsorbent hydrogel based on poly(acrylic acid-sodium acrylate-acrylamide)/sodium humate poly(AAc-SA-AM)/SH was applied as adsorbent to adsorb metal ions (Pb2+, Fe2+) from the aqueous solutions. The factors affecting adsorption capacity of the poly(AAc-SA-AM)/SH hydrogel such as contact time, pH, temperature, SH content (wt.%), initial concentration of the metal ion, and ionic strength were systematically investigated. Results from the experimental data revealed that an appropriate addition of SH (2.44 wt.%) not only increases the metal ion adsorption of poly(AAc-SA-AM) hydrogel but also improves its regeneration ability. The results showed that the adsorption equilibrium data fitted the Langmuir isotherm better than the Freundlich isotherm. The maximum binding capacity for Pb2+ ion was 198 and 164 mg/g/l for Fe2+ ion for per g of poly(AAc-SA-AM)/SH (SH4) hydrogel (high as compared to many other adsorbents). The changes in thermodynamic parameters were also calculated, and the negative Delta G degrees and Delta H degrees confirmed that the adsorption process was spontaneous and exothermic. The kinetic studies revealed that the adsorption process can be well described by the pseudo-second-order kinetic model.

The most commonly applied methods for the treatment of used adsorbents is to recover them in acid/alkaline medium or direct enflame them. This work dealt with a new potential and economic method to utilize a waste adsorbent. Poly(AAc/AM/SH) superabsorbent hydrogels have proved to be a good adsorbent for Cu2+ ions and after adsorption the hydrogels were recovered in acid medium. In this report, the Cu2+ ion adsorbed hydrogel has not undergone any regeneration process and applied directly to phosphate ion adsorption. The Cu2+ ions-loaded poly(AAc/AM/SH) hydrogels, were stable within a wide pH range and suitable for phosphate ion adsorption. The factors affecting the phosphate adsorption, such as pH, ionic strength, contact time, temperature, initial concentration of the phosphate ion, and coexisting ions were systematically investigated. The phosphate adsorption was highly pH dependent; and the maximum adsorption of 87.62 mg/g was achieved at pH 6.1. The adsorption data fitted the Langmuir adsorption isotherm better than the Freundlich isotherm. The concomitant anions show profounder adverse influence on phosphate ion adsorption of poly(AAc/AM/SH)-Cu hydrogel and the effect follows the order citrate > sulfate > bicarbonate > chloride > nitrate. The thermodynamic parameters including H degrees, G degrees, and S degrees for the adsorption processes of phosphate ions on the gel were also evaluated, and the negative G degrees and H degrees confirmed that the adsorption process was spontaneous and exothermic. The adsorption kinetic results suggest that the adsorption process was well described by the pseudo second-order kinetic model. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

A series of novel superabsorbent hydrogels based on acrylic acid (AAc), acrylamide (AM), and sodium humate (SH) were prepared by free-radical solution copolymerization for removal of dye and metal ion from waste water. Ammonium per sulfate was used as initiator and N,N' methylene bisacrylamide as crosslinker. The hydrogels were characterized with the help of FTIR and SEM. In this study the concentration of SH was varied in the range of 0.504.76 wt % based on total monomer content and the resulting hydrogels were investigated for the effect of SH on swelling and diffusion kinetic parameters such as equilibrium swelling ratio, initial swelling rate, swelling rate constant, maximum swelling at equilibrium, and type of diffusion, etc. Hydrogel having 2.43 wt % SH content showed the maximum water absorbency of 724 g of water per gram of hydrogel. Swelling exponent found in the range 0.680.79 thus suggesting Non-Fickian diffusion mechanism. The swelling behavior was also studied in different concentrations of salt solutions [sodium chloride (NaCl), magnesium chloride (MgCl2), and ferric chloride (FeCl3)]. The synthesized superabsorbent hydrogels were used for the adsorption of Cu2+ ions and methylene blue (MB) dye from their aqueous solutions. The influence of SH concentration on the Cu2+ ions and MB molecules binding capacity of hydrogels was tested. The chelation behavior was modeled using Langmuir isotherm. The maximum binding capacity for Cu2+ ion was 299 mg/L at 1000 mg/L, initial Cu2+ ion concentration and 269 mg/L at 320 mg/L, initial MB dye molecules concentration per gm of AAc/AM/SH containing 2.43 wt % SH content. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012