Browsing by Author "Sopanrao, Khandgave Santosh"

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Efficient copper removal using low-cost H3PO4 impregnated red-gram biochar-MnO2 nanocomposites
(Elsevier, 2023-02) Sopanrao, Khandgave Santosh
Copper metal removal from wastewater is an essential step to detoxify wastewater before release into human contact. To serve the same purpose, H3PO4 impregnated and KMnO4 functionalised, red-gram seed coat biochar is synthesized, for efficient and economic biosorption of aqueous copper ions. Response Surface Methodology (RSM) is employed to achieve a high optimal adsorption capacity of 493.34 mg/g, using a low adsorbent dosage of 0.6 g/L in only 90 min. Pre- and post-adsorption characterization of the adsorbent was done using XRD & XPS spectroscopy, FE-SEM, TGA and BET analysis to study its microstructure and mechanism of adsorption. A high mesoporous surface area of 207 m2/g and the negatively charged moieties on the surface help in complexation of the ions by reduced monolayer chemisorption. Cyclic regeneration of the adsorbent was studied to assess the adsorption efficiency, which retained a value as high as 70 % after 3 adsorption-desorption cycles.
Enhanced removal of Cu(II) and Ni(II) using MnOx-modified non-edible biochar: synthesis, characterization, optimization, thermo-kinetics, and regeneration
(Springer, 2023-06) Sopanrao, Khandgave Santosh
The remediation of copper and nickel heavy metals from industrial effluents is crucial to prevent environmental pollution and protect public health. Biosorption, a low-cost and eco-friendly technology, has gained increasing attention as an efficient method for the removal of heavy metals from effluent. In this work, a novel low-cost cocopeat biochar has been developed with appropriate chemical modification using KMnO4 to achieve high removal capacity and cyclic stability. Response surface methodology (RSM) was employed to identify optimal conditions and achieved as 1 g/L adsorbent dosage, 710 mg/L metal concentration, and 20-min contact time for Cu(II), and 2.85 g/L adsorbent dosage, 872 mg/L metal concentration, and 20 min contact time for Ni(II). A maximum adsorption capacity achieved as 291.54 mg/g and 181.16 mg/g for Cu(II) and Ni(II), respectively. Biosorbent exhibited a rapid kinetic process, with 86.44% and 77.61% adsorption occurring within just 20 min for Cu(II) and Ni(II), respectively. Brunauer–Emmett–Teller (BET) analysis showed a well-developed mesoporous molecular structure with an average pore diameter of 42.593 nm. The experimental results were fitted well with the pseudo-second-order and Langmuir isotherm, indicating monolayer adsorption primarily directed by chemisorption. Desorption efficiencies 48.25% and 52.16% for Cu(II) and Ni(II) respectively were achieved after four adsorption–desorption cycles. Furthermore, a preliminary study of chitosan composed of biochar was performed by experimental analysis and determination of optimum conditions of best performing synthesis methods using response surface methodology, biosorbent characterization, and possible mechanism of adsorption, which could potentially complement the removal of heavy metals from wastewater.
A mini-review on engineered biochars as emerging adsorbents in heavy metal removal
(Elsevier, 2023) Sopanrao, Khandgave Santosh
Environmental remediation using green adsorbents has been the primary focus of researchers worldwide to promote a sustainable and safe environment. Engineered biochars (E-BCs) from different biomass feedstocks have become highly successful adsorbents to remove heavy metals due to their conducive properties like large surface areas and enhanced functionalities, thereby giving higher removal efficiencies and cyclic stabilities. In this mini-review, an analysis with respect to synthesis, biosorption mechanism, modification methods, and performance comparison with respect to adsorption capacity (AC) of engineering biochars’s are discussed. The coconut shell (AC: 450.50 mg/g), pennisetum sp.straw-a weed species (AC: 763.12 mg/g), Douglas fir bark wood (AC: 127.20 mg/g), corncob (9.62 mg/g) are observed to be the best biosorbent for the heavy metal removal of Pb(II), Cd(II), Cr(VI), and As(V) from aqueous solution. The acid treatment, alkali treatment, salt treatment, oxides treatment, ball milling, steam activation, alumina nanoparticles, magnetic activation, chitosan modification, and nanoscale zero valent iron (nZVI) are the common modification methods to develop E-BC. The future challenges and prospects are also discussed.
Modified coal fly ash as a low-cost, efficient, green, and stable adsorbent for heavy metal removal from aqueous solution
(Springer, 2022-05) Sopanrao, Khandgave Santosh
The treatment of an industrial effluent contaminated with a high concentration of Ni(II) and Cu(II) was executed using naturally available biomasses. Low-cost adsorbents such as wheat bran (WB), calcium bentonite (CB), orange peel (OP), and fly ash (FA) were synthesized by different protocols and performed further modifications to remove Ni(II) and Cu(II). The highest removal efficiency for both metals was achieved by modified fly ash with zeolite (FA-Z). Physio-chemical characterization studies were performed using field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller (BET). The Barrett–Joyner–Halenda (BJH) results have indicated the adsorbent had dominant mesopores with a BET surface area of 346.62 m2/g. The effect of various operating factors on the metal removal by FA-Z was investigated and optimized using the central composite design (CCD) matrix of response surface methodology (RSM). The highest removal efficiency of Cu(II) and Ni(II) was 99.04% and 97.73%, respectively, at optimal conditions in the batch study. The highest removal efficiency for Cu(II) and Ni(II) was noticed at a bed height of 5 cm, initial concentration of 100 mg/L, and flow rate of 5 mL/min, which is equal to 99% and 96%, respectively in the column study. The Langmuir adsorption isotherm holds the best for Ni(II) with a maximum adsorption capacity of 60.69 mg/g, indicating monolayer adsorption is favorable, whereas, for Cu(II), Freundlich was found to be the best fit with a maximum adsorption capacity of 96.42 mg/g, shows the adsorbent surface is heterogeneous, and uptake of adsorbate as multi-layered. The kinetic study represented the pseudo-second-order (PSO) model was the best fit for both Cu(II) and Ni(II) sorption, suggesting a process to show chemisorption. The efficiency of modified fly ash with zeolite in removing Ni(II) and Cu(II) in multi-metal and real effluent was ~ 60% and ~ 95%, respectively. The FA-Z desorption was obtained up to 4 cycles, and the desorption efficiency of Cu(II) and Ni(II) metal ions achieved 95% and 93%, respectively.
Novel coal fly ash–chitosan composite for highly efficient, cost-effective and stable removal of lead and chromium from industrial wastewater
(RSC, 2025-06) Sopanrao, Khandgave Santosh
In the present study, a novel and economical adsorbent was synthesized from a coal fly ash–chitosan composite to remove Pb2+ and Cr6+ from aqueous solutions. The characterization of the adsorbent under optimal conditions revealed that it was mesoporous and rich in different functional groups, which enhanced its adsorption properties. The optimal conditions for the adsorption process were achieved at three levels. At the first level, the optimal conditions for fly ash calcination (300 °C for 2 h), H3PO4 concentration (0.4 mol L−1), MFA–CS ratio (3[thin space (1/6-em)]:[thin space (1/6-em)]1), and effective morphology (nanopowder) for Pb2+ and Cr6+ removal were achieved. At the second level, response surface methodology achieved adsorption capacities of 339.27 mg g−1 for Pb2+ removal and 242.84 mg g−1 for Cr6+ removal under optimal conditions. The third level involved pH standardization, which further enhanced the adsorption capacities to 352.19 mg g−1 for Pb2+ removal and 265.13 mg g−1 for Cr6+ removal. These results were well fitted by the pseudo-second-order kinetic and Langmuir isotherm models, demonstrating that the adsorption progressed via monolayer chemisorption. Removal efficiencies of 86.78% and 67.09% were obtained for Pb2+ and Cr6+, respectively, during their simultaneous removal. Thermodynamic studies confirmed the spontaneity of the adsorption process. The adsorbent demonstrated reusability, retaining its performance over 15 regeneration cycles. In column studies, maximum adsorption capacities of 255.61 mg g−1 for Pb2+ and 42.08 mg g−1 for Cr6+ were achieved, described well by the Thomas model. This cost-effective adsorbent, driven by ion exchange and surface complexation mechanisms, holds significant promise for wastewater treatment.
Novel phosphoric acid-modified biochar–chitosan nanocomposite for an efficient and cost-effective multimetal removal from wastewater
(ACS, 2025-09) Sopanrao, Khandgave Santosh
This study presented a novel and cost-effective adsorbent developed from phosphoric acid-modified biochar–chitosan nanocomposite for the efficient removal of Cu2+, Ni2+, and Zn2+ from wastewater. The biochar was synthesized at an optimized pyrolysis temperature of 550 °C for 2 h, followed by modification with phosphoric acid and composed of chitosan, resulting in a mesoporous PGB–CS composite (9.18 nm pore diameter) that exhibited a high surface area (167.98 m2/g), low crystallinity, good thermal stability, and abundant surface functional groups such as amine, carboxylic, and hydroxyl. The adsorption parameters were optimized using the Box–Behnken design of response surface methodology, obtaining maximum adsorption capacities of 221.56 mg/g for Cu2+, 175.47 mg/g for Ni2+, and 127.46 mg/g for Zn2+ under optimal conditions. The pH study further improved the adsorption capacities to 249.78 mg/g for Cu2+, 191.48 mg/g for Ni2+, and 145.91 mg/g for Zn2+. The adsorption process followed pseudo-second-order kinetics, indicating chemisorption, and confirmed the Langmuir isotherm, suggesting monolayer adsorption. Thermodynamic parameters confirmed the spontaneous and endothermic nature of the adsorption. Real industrial effluent from a battery manufacturing industry demonstrated removal efficiencies of 83.19% (Cu2+), 61.94% (Ni2+), and 52.34% (Zn2+). The adsorbent maintained stability and reusability over 8 regeneration cycles, with desorption efficiencies of 53.17%, 51.97%, and 51.07% for Cu2+, Ni2+, and Zn2+, respectively, using H2SO4, HNO3, and HCl. The synthesis cost was estimated as USD 8.13/g (Rs. 682.14/g), indicating strong economic potential. Adsorption mechanisms were attributed to surface complexation, ion exchange, and electrostatic attraction. The developed adsorbent provided a sustainable and efficient approach for treating heavy-metal-contaminated industrial wastewater.
Phosphoric acid–modified bentonite-chitosan composite beads: a novel and cost-effective adsorbent for multi-metal wastewater treatment
(Springer, 2024) Sopanrao, Khandgave Santosh
This study introduces a novel, cost-effective adsorbent made from phosphoric acid–modified bentonite-chitosan composite beads, designed to remove Cu2⁺, Ni2⁺, and Zn2⁺ from aqueous solutions. Characterization of the composite revealed a mesoporous structure and the presence of functional groups that enhance its adsorption properties. Using response surface methodology, the adsorption capacities were determined as 362.24 mg/g for Cu2⁺, 279.51 mg/g for Ni2⁺, and 210.54 mg/g for Zn2⁺ under optimal conditions. A pH study further improved the adsorption capacities to 381.29 mg/g for Cu2⁺, 305.98 mg/g for Ni2⁺, and 225.04 mg/g for Zn2⁺. The adsorption process followed pseudo-second-order kinetics and was best described by the Langmuir isotherm model, suggesting that the adsorption occurred on a single layer of the adsorbent surface via chemical bonds. In competitive adsorption scenarios, Cu2⁺ was removed more efficiently than Zn2⁺ and Ni2⁺. The removal efficiencies achieved were 88.59% for Cu2⁺, 72.30% for Ni2⁺, and 62.07% for Zn2⁺ using 1 g/l adsorbent within 30 min for treating industrial effluent. Thermodynamic analysis confirmed that the adsorption process was spontaneous and endothermic. The adsorbent maintained good performance over 10 regeneration cycles, demonstrating its reusability. The primary adsorption mechanisms include electrostatic attraction, surface complexation, and ion exchange. The developed adsorbent proved to be an efficient, sustainable, and environmentally friendly solution for removing heavy metals from wastewater. This cost-effective material can be readily implemented in industrial wastewater treatment plants to tackle heavy metal contamination.
Polyvinyl alcohol modified chitosan composite as a novel and efficient adsorbent for multi-metal removal
(Elsevier, 2024-07) Sopanrao, Khandgave Santosh
This study focussed on the development of a novel and efficient adsorbent derived from polyvinyl alcohol-modified chitosan composite for the removal of Cu+2, Ni+2, and Zn+2 from wastewater. The characterization of composite exhibits mesoporous, thermal stability, and rich with functional groups. The Box-Behnken method of Response Surface Methodology framework was employed, and attained optimum conditions for Cu+2 (1000 mg/l, 20 min, 1 g/l), Ni+2 (1000 mg/l, 20 min,1 g/l), and Zn+2 (972.28 mg/, 20 min, 1 g/l) respectively. Langmuir isotherm and Pseudo-Second order kinetic model best fit, indicating chemisorption-driven monolayer adsorption and achieved maximum adsorption capacity 303.29 mg/g, 209.08 mg/g, and 173.39 mg/g for Cu+2, Ni+2, and Zn+2 respectively. In competitive adsorption of binary and ternary systems, Cu+2 displayed superior removal efficiency compared to Ni+2 and Zn+2. Furthermore, the adsorbent's efficacy was evaluated using industrial effluent, demonstrating higher removal efficiency for Cu+2 (79.09 %) compared to Ni+2 (50.73 %) and Zn+2 (46.97 %). Thermodynamic study (Enthalpy: 19.08 to 26.29 kJ mol−1, Gibb’s free energy: −0.32 to − 3.10 kJmol−1, Entropy: 65.10 to 90.95 J mol−1 K−1) underlined the spontaneity and endothermic nature of adsorption. The desorption efficiency ranging from 88.94 % to 48.90 %, 88.19 % to 41.31 %, and 84.09 % to 48.19 % up to 10th cycles for Cu+2, Ni+2, and Zn+2 using 0.4 mol/l H2SO4, 0.6 mol/l HNO3, and 0.6 mol/l HCl respectively. The adsorption mechanisms, primarily surface complexation, ion exchange, and electrostatic attraction, prevail over physisorption. The PVA-CS, recognized as highly efficient and environment friendly adsorbent provides a practical solution for water decontamination.
Sustainable Zn2+ removal using highly efficient, novel, and cost-effective chitosan-magnetic biochar composite
(Springer, 2024-05) Sopanrao, Khandgave Santosh
This study focused on the development of a sustainable and low-cost adsorbent derived from the chitosan-biochar composite for the removal of Zn2+ from an aqueous solution. Biochar was prepared from cotton stalk residue by pyrolysis at 600 °C for 2 h, modified with FeCl3, and composed with chitosan in various ratios (1:3, 1:1, 3:1), leading to the formation of an efficient, thermally stable, and rich with functional groups chitosan-biochar composite denoted as CHB-Fe-CS. Functional groups (hydroxyl, carboxyl, and amine) were identified as key contributors to the adsorption mechanism. Langmuir isotherm (R2 = 0.99) and Pseudo-Second order (R2 = 0.99) were best fitted models with the experimental results indicating chemisorption-driven monolayer adsorption. The results revealed CHB-Fe-CS (3:1) composite obtained the highest adsorption capacity of 117.50 mg/g for Zn2+ under optimal conditions viz., 180 min batch time, 500 mg/l metal concentration, 4 g/l adsorbent dosage, 40 °C solution temperature, and 5.0 pH. Regeneration of the used adsorbent was performed using 0.2 mol/l HCl and obtained desorption efficiency of 67.48% and 51.48% after the 4th and 8th cycles. The adsorption mechanisms were dominated by ion exchange, surface complexation, and electrostatic attraction compared to intra-particle diffusion and physisorption. The CHB-Fe-CS demonstrated an economical, environment friendly, and good performing adsorbent for water decontamination.