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Utilization of whole lignocellulosic biomass waste to synthesize value-added functional materials is an appealing approach both from economic and environmental viewpoints. In the present study, a simple synthetic protocol was employed to convert fallen dry forest lignocellulosic biomass, i.e. whole pine needles (WPN), into a cost-effective and effective dye adsorbent. The alkaline treatment of WPN was performed using sodium hydroxide, and the resultant alkali-treated WPN (AWPN) was explored as adsorbent using a range of dyes. Batch experiments were conducted to optimize various parameters, viz. including initial dye concentrations. Amidst range of dyes studied, AWPN showed maximum adsorption of malachite green (MG). The maximum adsorption was obtained with MG %removal (>95%) within 30 min. The adsorbent (loaded and unloaded) was characterized through various analytical techniques. Fitting of the kinetic data to pseudo-second-order model implied that adsorption was via the chemisorption mechanism. Validity of kinetic model fitness was further confirmed by low chi-square (χ2) and normalized standard deviation (Δq%) values. Isotherm studies followed Langmuir isotherm signifying monolayer adsorption with Langmuir maximum adsorption capacity (qm) of 377.36 mg/g. AWPN is regenerable and reusable for six cycles with appreciable cumulative adsorption capacity of 1093.99 mg/g. With rapid and effective adsorption capacity, the main highlight of the synthesized adsorbent was its simple modification involving minimal use of chemicals that ensures cost-effectiveness and no energy consumption. [ABSTRACT FROM AUTHOR]

This study explores the application of ZnO-ZnFe2O4 composite nanofibers for the adsorption of Malachite Green (MG) dye from water. The composite nanofibers were fabricated using simple polyvinylpyrrolidone (PVP) mediated electrospinning method by changing zinc and iron precursor weight ratio named as Zn–Fe (1-1), Zn–Fe (2–1) and Zn–Fe (1–2). The diameter of 1D nanofibers was found to be 40–60 nm. The formation of hexagonal wurtzite structure of ZnO and cubic spinel structure of ZnFe2O4 was confirmed by XRD and HRTEM analysis. The effects of various parameters such as pH, contact time and initial concentration on the adsorption process were investigated. The Zn–Fe (1-1) nanofibers showed higher adsorption efficiency than other two. The adsorption results demonstrated excellent adsorption performance, with a maximum adsorption capacity of 146.77 mg/g at pH = 7 for Zn–Fe (1-1). Furthermore, the adsorption kinetics and isotherms were analyzed to understand the adsorption mechanism and equilibrium behaviour. It was found that the nanofibers material can be recycled and reused up to five cycles.

Malachite green (MG) is used for the dyeing of cotton, paper, and jute, among other materials, and presents acute toxicity to a wide range of aquatic and terrestrial animals. A polyacrylamide (PA) hydrogel modified with a low content of oxygenated and aminated carbon nanomaterials may be a suitable candidate to adsorb MG from wastewater. Herein, graphene oxide and carbon nanotubes (CNTs) were incorporated during the in situ polymerization of PA. The hydrogels were characterized through thermogravimetry, differential scanning calorimetry and infrared spectroscopy as well as imagined by scanning electron microscopy. The swelling and adsorption capacity were investigated to explore the influences of different carbon dimensionalities (1D and 2D), zeta potentials and nanofiller concentrations on the adsorption behavior of the hydrogel. There was an increase of approximately 1500% in the adsorption capacity after 24 h of exposure of a hydrogel with graphene oxide (GO) at 0.25 wt% with respect to the neat PA. Aminated graphene produced similar gains in the adsorption capacity of the GO-hydrogel, although it presents a positive zeta potential that is the opposite of that of GO. The modified CNTs showed smaller gains in the adsorption capacity, reaching a maximum 400% increase with respect to the PA hydrogel. The main factors that seem to affect the adsorption capacity were the dimensionality and degree of functionalization. The graphene oxide-based nanofillers were 3 to 4 times more functionalized than the nanotubes. The adsorption results were adjusted with a pseudo-second order kinetic model that allowed a complementary discussion about the nature of the physico-chemical effects on the process of MG adsorption in the hydrogel nanocomposites. [ABSTRACT FROM AUTHOR]

In this study, bacterial cellulose (BC) and BC/locust bean gum (LBG) composite produced from banana hydrolysate were both used as the adsorbent for various organic dyes adsorption especially for malachite green (MG) adsorption for the first time. The BC/LBG(2%) composite exhibited significantly enhanced swelling rate and textural characteristics while maintained the basic structure of BC as depicted by XRD, FT-IR, and NMR, providing a foundation for its application as an excellent adsorbent. The composite exhibited a high adsorption rate and adsorption capacity for MG (exceeding 95 % and 2000 mg/g), and had a good selectivity for MG adsorption in the solution containing crystal violet (CV), rhodamine B (RB), and methyl orange (MO). The MG adsorption process conformed to multiple models including Langmuir and pseudo-first-order models. And the adsorption mechanism mainly comprised chemical adsorption (hydrogen bonding and electrostatic interactions) and physical adsorption. The reusability of BC/LBG(2%) composite was attractive for industrial application that the MG adsorption rate reduced merely a little (still higher than 88 %) after the 5th regeneration process. Overall, considering its adsorption capacity, selectivity, and reusability, BC/LBG(2%) composite prepared by in-situ fermentation with LBG addition was a competent adsorbent for MG adsorption and MG containing wastewater treatment. [Display omitted] • BC/LBG(2%) composite was prepared by in-situ fermentation in banana hydrolysate. • This material was a competent adsorbent for MG adsorption. • High adsorption rate (> 95 %) and adsorption capacity (> 2000 mg/g) were fulfilled. • The adsorbent had a good selectivity for MG adsorption in multi-component system. • The adsorbent had a good reusability after regeneration by hydrothermal treatment. [ABSTRACT FROM AUTHOR]

The coconut-based agricultural wastes have gained wide attention as an alternative adsorbent for the removal of diverse pollutants from the industrial effluents. This paper presents the zinc chloride activation of adsorbent carbon and the utilization as an adsorbent for the removal of malachite green dye from aqueous solution. The characterisation of activated carbon was performed to get an insight into the adsorption mechanism. The ZnCl2 activated carbon acquired a higher specific surface area (544.66 m2 g−1) and stability (−32.6 mV). The impact of process parameters including contact time (20–220 min) and initial dye concentration (20–80 mg L−1) were evaluated on the effectiveness of activated carbon for dye removal. The results concluded that zinc chloride activated carbon showed a significant dye adsorption (39.683 mg g−1) at an initial concentration of 20 mg L−1 after 3 hours. Based on the correlation coefficient (R2), the Freundlich isotherm model (0.978–0.998) was best fitted for the experimental data followed by the intraparticle diffusion model (0.88–0.929) as the most appropriate model for malachite green dye removal. Additionally, the energy and thermogravimetric analysis portrayed the suitability of the carbon material to be used as an energy alternative to coal.

In this study, an effective adsorbent was synthesized to remove malachite green (MG), which is one of the toxic dyes. Firstly, single walled carbon nanotube with carboxylated acid (SWCNT-COOH) was functionalized with diethylenetriamine and a new nanocomposite was obtained using nano zinc oxide (ZnO) powder. The effects of pH (3–7), the amount of adsorbent (5–15 mg) and the initial concentration (10–50 mg L–1) of the solution on the adsorption uptake were investigated. The optimal parameters that maximize the adsorption uptake according to the specified working range are found to be 4.63 for pH, 49.94 mg L–1 for initial concentration, 5.25 mg for the adsorbent dose, and the maximum adsorption capacity has been found as 52.26 mg g–1. The excellent fitting of the pseudo-second kinetic model with (R² = 0.9912) was fitted the experimental data. The Freundlich isotherm model gave a clue about the type of adsorption. Furthermore, thermodynamic results showed that adsorption process was endothermic. [ABSTRACT FROM AUTHOR]

The widely used toxic dye malachite green (MG) poses a significant risk to human health, having a mutagenic effect. Waste date stones were used to produce microwave‐activated carbons and were applied to adsorb the highly toxic dye. The critically important task of selecting the correct design adsorption capacity for different effluent pollutant concentrations to meet effluent discharge limit standards is described and a novel design selection criteria approach is presented. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The boron doped mesoporous carbon nitride was synthesized as a new adsorbent. • The adsorbent was applied to efficient removal of the malachite green from water. • The adsorbent with 1 wt% doped boron showed the highest adsorption capacity. • Dye concentration, adsorbent weight, pH, and temperature were optimized by RSM. • The reusability of the adsorbent was checked in at least six cycles. Abstract In this study the adsorption performance of boron doped mesoporous carbon nitride (BMCN) was studied for the elimination of malachite green (MG) dye from wastewater. BMCN with various weight ratios of boron doping was prepared in two steps including using a hard template to synthesize MCN, and then addition of boric acid as the boron source to produce BMCN. 1 wt% boron doping displayed the highest removal efficiency and adsorption capacity. The new adsorbent was analyzed using XRD, N 2 adsorption-desorption, TEM, SEM-EDX and its elemental mapping, and FT-IR. Four critical parameters optimized by response surface methodology (RSM) method were temperature, initial dye concentration, pH and sorbent weight for MG adsorption. The maximum removal (100%) predicted from RSM was reported for 18 mg of the sorbent at pH 5 and MG concentration of 20 mg L−1 at room temperature. The boron doped mesoporous carbon nitride showed a high maximum adsorption capacity about 310 mg g−1 and reached at the equilibrium within 30 min followed the pseudo-second-order kinetic model with 99.8% MG removal while the rate-limiting step is the intraparticle diffusion stage. The adsorption phenomena matched well to the heterojunction surface Freundlich, Koble-Corrigan, and Sips isotherm models. The BMCN1 showed excellent reusability and was applied for six cycles of regeneration effectively, while its removal efficiency remained at a high value. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Magnetic particle is a promising class of materials to absorb harmful contaminants for their easy collecting property with magnetic response. Here, we report a novel kind of polycarboxylic magnetic polydopamine sub-microspheres (Fe 3 O 4 @PDA-COOH) facilely synthesized by coating polydopamine (PDA) onto the surface of magnetic nanocrystal clusters (Fe 3 O 4). Then the sub-microspheres were modified with mercaptosuccinic acid (MSA) to have polycarboxylic groups on their surface. Fourier transform infrared spectroscopy (FT-IR) was used to demonstrate the desired chemical structure. The unique morphology and particle size distribution were confirmed by Transmission electron microscopy (TEM). Malachite green (MG) was used as a model to test the adsorption capacity of the magnetic sub-microspheres. Besides, factors such as initial MG concentration, initial solution pH, and contact time were systematically studied for this adsorption process. Results showed that the maximum adsorption capacity of Fe 3 O 4 @PDA-COOH could reach up to 331.0162 mg/g (MG/ sub-microspheres), much higher than that of Fe 3 O 4 @PDA. The adsorption kinetics and adsorption isotherms could be well described by pseudo-second-order kinetic model and Freundlich isothermal model. Moreover, Fe 3 O 4 @PDA-COOH sub-microspheres can retain the high adsorption ability after five using-cycles. Therefore, the synthesized Fe 3 O 4 @PDA-COOH can be a high-efficiency adsorbent in the field of wastewater treatment. [ABSTRACT FROM AUTHOR]