Modified biochar from Moringa seed powder for the removal of diclofenac from aqueous solution.

In this study, Moringa seed powder (MSP) was pyrolyzed at 450 °C to synthesize Moringa seed powder biochar (MSPB) and treated with phosphoric acid (H3PO4) to synthesize phosphate-modified Moringa seed powder biochar (MSPB-HPO) as an adsorbent for the removal of diclofenac (Dfc) from aqueous solution. Fourier transform infrared (FTIR) analysis, energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), and pH point of zero charge (pHpzc) were conducted to give more insight into the adsorbent's properties. The SEM analysis showed the transformations in the surface morphology from the parent material to the synthesized materials after the thermal and acid treatment. EDS analysis revealed the variation in the elemental composition of the materials prior to and after adsorption of Dfc ions. The FTIR analysis showed changes and peak intensities of functional groups involved in Dfc removal. The pHpzc showed the charge carried by MSPB-HPO in different pH conditions. Isotherm data best matched the Sips model, and the pseudo-second-order model best described the adsorption kinetics. The maximum adsorption capacity of MSPB-HPO by Sips model was found to be 100.876 mg g-1.

Synthesis of clay-cellulose biocomposite for the removal of toxic metal ions from aqueous medium.

Clay-cellulose biocomposite (CCB) was synthesized in the present study. Spin and pressure-induced heating was applied to aggregate exfoliated clay tubules and cellulose using polyethylene glycol as an intermediate. The synthesized CCB was modified in the presence of NaOH at high temperature to obtain negative surface charge on the adsorbent. Physico-chemical properties of CCB were evaluated using different characterization techniques including Fourier transform infrared (FT-IR) and X-ray photoelectron (XPS) spectroscopy. The efficiency of the synthesized biocomposite for Pb(II) and Cd(II) removal from water was studied via laboratory scale experiments. The adsorption kinetics of Pb(II) and Cd(II) onto CCB was well described by the pseudo-second-order kinetic model. The maximum Langmuir adsorption capacity of CCB was found to be 389.78 and 115.96 mg g-1 for Pb(II) and Cd(II), respectively. Fixed-bed column studies were conducted for the adsorption system to compare the adsorption performance of CCB in continuous mode.

A comparative study of magnetic chitosan (Chi@Fe3O4) and graphene oxide modified magnetic chitosan (Chi@Fe3O4GO) nanocomposites for efficient removal of Cr(VI) from water.

Magnetic chitosan (Chi@Fe3O4) nanocomposite was synthesized and modified with graphene oxide (Chi@Fe3O4GO) and the potential of both materials as adsorbents was assessed for the removal of chromium (Cr(VI)) from water. The physico-chemical characteristics of magnetic nanocomposites were studied by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), x-ray diffraction (XRD), Raman spectroscopy and Brunauer-Emmett-Teller (BET). The synthesized adsorbents exhibited varied Cr(VI) removal efficiency at solution pH 2. The reaction kinetics correlated well with the pseudo-second-order model. The maximum adsorption capacity was found to be 142.32 and 100.51 mg g-1 for Chi@Fe3O4 and Chi@Fe3O4GO, respectively. Analysis of thermodynamic parameters suggested that the reaction occurred spontaneously and was endothermic in nature. Reusability studies showed that the adsorbents can be reused for up to four cycles of regeneration. Fixed bed column experiments revealed that the adsorption performance of Chi@Fe3O4 was affected by the flow rate, adsorbent loading and influent metal ion concentration. The results suggest that the prepared adsorbents have the potential to be used in removing Cr(VI) ions from contaminated water.

Facile functionalization of cellulose from discarded cigarette butts for the removal of diclofenac from water.

In this study, cellulose nanocrystals (CNCs), and cellulose nanofibers (CNFs) were extracted from discarded cigarette butts (DCBs), and investigated for their efficiency for diclofenac (Dfc) removal from water. CNFs extraction process involved cleaving of acetyl group by alkali treatment and etched with phosphate ions (HPO) from phosphoric acid to obtain the variably charged HPO-CNFs. To obtain CNCs, sulfuric acid was used to cleave phenol moieties from CNFs under high temperature and agitation. SEM, FT-IR, SEM-EDS, Raman spectroscopy were used to analyze the physico-chemical properties of synthesized cellulose materials. The SEM images revealed the exfoliated fiber strands of CNFs after extraction procedure, and the difference in the crystal structure of CNCs30 and CNCs60. The EDS analyses revealed the presence of higher amount of carbon in DCBs compared to other forms of synthesized celluloses. The FT-IR analyses revealed functional group shifts and bond reductions after various treatment steps, while the HPO attachment on the CNFs surfaces was confirmed by the presence of PO bonds. Raman analyses revealed clear crystals in the CNCs60 compared to the other celluloses. The adsorption capacity of HPO-CNFs for diclofenac removal was found to be 107.90 mg g-1 and Langmuir model fitted well to the adsorption data.

Synthesis of S-ligand tethered cellulose nanofibers for efficient removal of Pb(II) and Cd(II) ions from synthetic and industrial wastewater.

Cellulose nanofibers (CNFs) tethered with sulphur as anionic ligand were synthesized from medical absorbent cotton by dissolution with NaOH, CO(NH2)2 followed by mechanical intrusion of sulphur from SC(NH2)2 at an elevated temperature. The solid-phase CNFs embedded with sulphur complexes possessed negative sites which were used to remove cationic metals viz., Pb(II) and Cd(II) from synthetic and industrial wastewater. The physicochemical properties of the CNFs were analyzed by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), pH at point of zero charge (pHpzc) and X-ray photoelectron spectroscopy (XPS). Batch adsorption studies were conducted with synthetic wastewater to optimize the conditions for Pb(II) and Cd(II) removal by CNFs. Different adsorption kinetic models were applied to assess and define the adsorption mechanism. The maximum Langmuir adsorption capacity was found to be 1.16 and 0.82 mmol g-1 for Pb(II) and Cd(II) ions, respectively. Regeneration studies showed that the CNFs can be reused using 0.1 M NaOH as eluent. The percentage removal efficiency of different cationic metals by CNFs from untreated industrial wastewater ranged from ca. 90-98%.

Pretreatment assisted synthesis and characterization of cellulose nanocrystals and cellulose nanofibers from absorbent cotton.

In this work, cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs) were synthesized from absorbent cotton. Two pretreatments viz. dewaxing and bleaching with mild alkali were applied to the precursor (cotton). Acid hydrolysis was conducted with H2SO4 and dissolution of cotton was achieved with a mixture of NaOH-thiourea-urea-H2O at -3°C. Synthesized cellulose samples were characterized using FTIR, XRD, SEM, BET, and zeta potential. It seems that synthesis conditions contributed to negative surface charge on cellulose samples and CNCs had the higher negative surface charge compared to CNFs. Furthermore, BET surface area, pore volume and pore diameter of CNCs were found to be higher as compared to CNFs. The dewaxed cellulose nanofibers (CNF D) had a slightly higher BET surface area (0.47m2/g) and bigger pore diameter (59.87Å) from attenuated contraction compared to waxed cellulose nanofibers (CNFW) (0.38m2/g and 44.89Å). The XRD of CNCs revealed a semi-crystalline structure and the dissolution agents influenced the crystallinity of CNFs. SEM images showed the porous nature of CNFs, the flaky nature and the nano-sized width of CNCs. Synthesized CNF D showed a better potential as an adsorbent with an average lead removal efficiency of 91.49% from aqueous solution.