Removal of arsenic from aqueous solution using polyaniline/rice husk nanocomposite

Design and characterization of PANI/starch/Fe2O3 bio composite for wastewater remediation

A new synthesized polyaniline/starch/hematite bio composite (PANI/S/Fe₂O₃ BC) has been studied as an effective material for on-site water remediation. PANI/S/Fe₂O₃ BC was developed by combining the techniques of co-precipitation and interfacial polymerization in the presence of aqueous starch solution in an acidic medium under ultrasonic irradiation. The nano-morphologies and structures of the designed PANI/S/Fe₂O₃ BC were evaluated by various techniques relative to PANI and Fe₂O₃ nanoparticles. In single and multiple systems, PANI/S/Fe₂O₃ BC was evaluated as a possible adsorbent for different heavy metals, including As³⁺, Zn²⁺, and Co²⁺, relative to PANI and Fe₂O₃ nanoparticles. In terms of pH value, operating temperature, initial heavy metal concentration, contact time, adsorbent dose and competitive ions in the solutions, the adsorption process was optimized. For 92% overall adsorption of Co²⁺ and 100% overall adsorption of both As³⁺ and Zn²⁺, the adsorption equilibrium was achieved within 60 and 120 min, respectively. In addition, adsorption thermodynamic analysis shows that the As³⁺ ions adsorption process was not random and the pseudo-second-order fitted with experimental results. Moreover, PANI/S/Fe₂O₃ BC was evaluated as an antibacterial agent against Gram-negative bacteria (Salmonella typhimurium) and Gram-positive bacteria (S. aureus, Methicillin-Resistant Staphylococcus, Aureus Clinical isolate and Bacillus subtilis). The reported performances indicated that the PANI/S/Fe₂O₃ BC is a potent candidate for industrial water bioremediation.

Chemically modified rice husk as an effective adsorbent for removal of palladium ions

Bio-matrix of rice husk and Mobil Composition of Matter No. 41 (MCM-41) was modified with alizarin red S for preconcentration of Pd²⁺ prior flame atomic absorption spectrometric determination. The prepared bio-matrix (RH@MCM-41@ARS) was characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope, energy dispersive X-ray spectrometer (SEM/EDX) and surface area studies. The impact of different parameters (solution pH, amount of sorbent, contact time, sample volume, initial Pd²⁺ concentration and diverse ions) on the uptake of Pd²⁺ were evaluated. The maximum adsorption capacity of Pd²⁺ onto RH@MCM-41@ARS was 198.2 mg g^-1 at optimum conditions. Applying the optimized procedure as a preconcentration step led to limit of detection of 0.13 μg L^-1 and dynamic analytical range up to 500 μg L^-1. The sorbent was regenerated by 0.5 mol L^-1 thiourea for at least 10 cycles without significant reduction of adsorption capacity. The method was applied for preconcentration of Pd²⁺ from real samples.

Hollow Polyaniline Microsphere/Fe3O4 Nanocomposite as an Effective Adsorbent for Removal of Arsenic from Water

Polyaniline hollow microsphere (PNHM)/Fe₃O₄ magnetic nanocomposites have been synthesized by a novel strategy and characterized. Subsequently, PNHM/Fe₃O₄-40 (Fe₃O₄ content: 40 wt.%) was used as an adsorbent for the removal of arsenic (As) from the contaminated water. Our investigations showed 98–99% removal of As(III) and As(V) in the presence of PNHM/Fe₃O₄-40 following pseudo-second-order kinetics (R² > 0.97) and equilibrium isotherm data fitting well with Freundlich isotherm (R² > 0.98). The maximum adsorption capacity of As(III) and As(V) correspond to 28.27 and 83.08 mg g⁻¹, respectively. A probable adsorption mechanism based on X-ray photoelectron spectroscopy analysis was also proposed involving monodentate-mononuclear/bidentate-binuclear As-Fe complex formation via legend exchange. In contrast to NO₃⁻ and SO₄²⁻ ions, the presence of PO₄³⁻ and CO₃²⁻ co-ions in contaminated water showed decrease in the adsorption capacity of As(III) due to the competitive adsorption. The regeneration and reusability studies of spent PNHM/Fe₃O₄-40 adsorbent showed ~83% of As(III) removal in the third adsorption cycle. PNHM/Fe₃O₄-40 was also found to be very effective in the removal of arsenic (<10 μg L⁻¹) from naturally arsenic-contaminated groundwater sample.

Heavy Metal(loid) Remediation Using Bio-Waste

Heavy metal(loid)s are hazardous, biologically non-essential, non-biodegradable and persistent in nature, which can accumulate in plants and animals as well as in environment especially agri- and aqua- culture ecosystems. It is severely responsible for causing several health hazards problems in human, such as, cardiovascular, pulmonary, hepatic, nephrological, dermatological, neurological disorders as well as carcinogenic effects. Removal of these heavy metals from living systems is extensively expensive and also unsuccessful in sent percent removal. Therefore, in order to protect the environment, the removal of heavy metal(loid)s from polluted effluents is essential before discharging into environment. Besides various treatment technologies, sorption of metal(loid)s using bio-wastes are highly potent alternatives in recent years. The present chapter deals with the removal efficiencies of various bio-wastes, orange peels, waste tea leaves, rice husk, wheat stalk, sugar cane bagasse, coconut husk, sun flower stalk, corn cob, nut shell, water hyacinth, crab shell particle, activated carbons etc. The present discussion has also revealed that bio-waste could be a low-cost eco-friendly and green emerging alternative technology in treating the metal(loid)s contaminated environment without posing any further adverse environmental impacts.

Use of core-shell polyaniline/polystyrene nanocomposite for removal of Cr (VI)

In this study the ability of polyaniline/polystyrene as high performance synthetic adsorbent for the adsorptive removal of Cr (VI) ions from aqueous solutions was investigated. To carry out the investigation, the batch operation method was employed. As well, the effects of various experimental parameters like pH, adsorbent dosage, contact time and the temperature on the removal efficiency were studied. The optimum conditions for Cr (VI) removal are achieved with pH 4, adsorbent dosage of 15 g L−1, and 30 min equilibrium time. It is worth noting that the adsorption of Cr (VI) followed pseudo-second-order kinetics. The equilibrium adsorption isotherm was better described by Temkin adsorption isotherm model. The adsorption capacity ( qmax) of PAn/Ps for Cr (VI) ions in terms of monolayer adsorption was 19 mg g−1. The change of entropy (▵S0) and enthalpy (▵H0) were estimated to be −0.08455 J (mol K)−1 and −29.04 kJ mol−1, respectively. The negative value of Gibbs free energy (▵ G0) indicates feasible and spontaneous adsorption of Cr (VI) on PAn/Ps.

Use of core-shell polyaniline/polystyrene nanocomposite for removal of Cr (VI)

In this study the ability of polyaniline/polystyrene as high performance synthetic adsorbent for the adsorptive removal of Cr (VI) ions from aqueous solutions was investigated. To carry out the investigation, the batch operation method was employed. As well, the effects of various experimental parameters like pH, adsorbent dosage, contact time and the temperature on the removal efficiency were studied. The optimum conditions for Cr (VI) removal are achieved with pH 4, adsorbent dosage of 15 g L−1, and 30 min equilibrium time. It is worth noting that the adsorption of Cr (VI) followed pseudo-second-order kinetics. The equilibrium adsorption isotherm was better described by Temkin adsorption isotherm model. The adsorption capacity ( qmax) of PAn/Ps for Cr (VI) ions in terms of monolayer adsorption was 19 mg g−1. The change of entropy (▵S0) and enthalpy (▵H0) were estimated to be −0.08455 J (mol K)−1 and −29.04 kJ mol−1, respectively. The negative value of Gibbs free energy (▵ G0) indicates feasible and spontaneous adsorption of Cr (VI) on PAn/Ps.