Adsorption performance of activated carbon synthesis by ZnCl2, KOH, H3PO4 with different activation temperatures from mixed fruit seeds

In this study, new activated carbons (ACs) were synthesized from a mixture of lemon and orange seeds (LOS) for toxic metal removal from aqueous solutions. Adsorbents have been produced by chemical activation with different activation agents (with H₃PO₄, ZnCl₂ and KOH) and activation temperature (600°C, 700°C, 800°C). The elemental analysis, FT-IR, XRD and SEM analyses were performed to determine the characterization of the ACs. A series of batch adsorption experiments were done to research the influence of various parameters such as pH, adsorbent dosage, contact time, temperature, the complexing agents on the toxic metal ions (Cu(II), Cr(III) and Ni(II)) removal capacity of ACs. Adsorption equilibration time was 60 min, the adsorption capacity was 118.02 mg/g for Ni(II) ions, 146.03 mg/g for Cr(III) ions and 150.45 mg/g for Cu(II) ions. The adsorption of toxic metal ions was observed as a maximum at pH = 5 on AC-ZnCl₂ (600°C) produced under N₂ atmosphere. The adsorption process was fitted with a Langmuir isotherm model and a pseudo-second-order kinetic equation, showing the metal ions adsorption on AC was monolayer coverage. Thermodynamic studies show that the adsorption is endothermic and spontaneous in nature. AC produced from the LOS mixture has not been encountered in the literature. A simple, easy-to-apply method has been developed for a new adsorbent prepared from a mixture of LOS with environmentally friendly, easy to produce, reusable, cost-effective, non-toxic and with good adsorption-desorption capacity. Therefore, this study will contribute to the world economy in terms of environmental and wastewater cleaning.

Development of Carbon Nanotubes (CNTs) Membrane from Waste Plastic: Towards Waste to Wealth for Water Treatment

Plastic, a non-biodegradable material has always been a concern to the environment and people. This single-use item generates waste to landfills and it persists for centuries once disposed. The urge of transforming such material into a highly valuable product has sought attention from many researchers. This study emphasizes on a nanotechnological approach to synthesize vertically-aligned carbon nanotubes (CNTs) on a substrate template using commercially available plastic bags as carbon precursor. CNTs are grown inside a hexagonally arranged nanoporous anodic alumina membranes (NAAMs). CNTs are liberated by wet chemical etching to dissolve the alumina matrix. The resulting CNTs are used as adsorption media filters for water treatment purpose. The high adsorption affinity towards heavy metals, organic matters and microbes, ability to antifouling and self-cleaning function have made CNTs a better choice over others. This article briefly discusses the catalyst-free synthesis, growth mechanism, characterization and functionalization of CNTs for water treatment application.

Ag/RGO Photocatalyst for Methyl Orange Treatment

In present study, a simple chemical method for the synthesis of silver-reduced graphene oxide (AG/RGO) nanocomposite was reported. The objective is to evaluate the performance of AG/RGO in photocatalytic degradation activity of methyl orange (MO) under artificial visible light source. The synthesized catalyst was then characterized using field emissions scanning electron microscope with energy dispersive X-Ray spectroscope (FESEM-EDX), photoluminescence spectroscopy (PL) and UV-visible spectroscope (UV-VIS) to determine the morphology, physical and chemical composition of the photocatalyst. The characterization results show the synthesized catalyst possess nanometre dimension silver nanoparticles (AgNPs) were deposited on reduced graphene oxide sheets. The photocatalytic activity of 0.3 g AG/RGO obtained through the degradation of 5 mg/l MO is 93.74% with a degradation rate of 3.1 × 10-2 min-1.

Study of Mercury [Hg(II)] Adsorption from Aqueous Solution on Functionalized Activated Carbon

Mercury and its compounds are toxic substances, whose uncontrolled presence in the environment represents a danger to ecosystems and the organisms that inhabit in it. For this reason, in this work, we carried out a study of mercury [Hg(II)] adsorption from aqueous solution on functionalized activated carbon. The activated carbons were prepared by chemical activation of a mango seed with solutions of CaCl₂ and H₂SO₄ at different concentrations, later, the carbonaceous materials were functionalized with Na₂S, with the aim of increasing the sulfur content in the carbonaceous matrix and its affinity to mercury. The materials were characterized using: proximal analysis, scanning electron microscopy, Boehm titrations, point zero charge (pH_PZC), and infrared spectroscopy. Additionally, immersion calorimetries were performed in the mercury solution. The results of textural and chemical characterization show materials with low Brunauer-Emmett-Teller (BET) surface areas between 2 and 33 m²·g^-1 and low pore volumes. However, they had a rich surface chemistry of oxygenated groups. The enthalpies of immersion in the mercury solutions are between -31.71 and -77.31 J·g^-1, showing a correlation between the magnitude of the enthalpic data and the adsorption capacity of the materials. It was evidenced that the functionalization process produces a decrease in the surface area and pore volume of the activated carbons, and an increase in the sulfur content of the carbonaceous matrix. It was evidenced that the functionalization process generated an increase in the mercury [Hg(II)] adsorption capacity between 21 and 49% compared to those of the nonfunctionalized materials, reaching a maximum adsorption capacity of 85.6 mgHg²⁺g^-1.

Adsorption of Hg(II) in an Aqueous Solution by Activated Carbon Prepared from Rice Husk Using KOH Activation

With the development of industry, the discharge of wastewater containing mercury ions posed a serious threat to human health. Using biomass waste as an adsorbent to treat wastewater containing mercury ions was a better way due to its positive impacts on the environment and resource saving. In this research, activated carbon (AC) was prepared from rice husk (RH) by the KOH chemical activation method. The characterization results of scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), Fourier transform infrared (FTIR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) showed that rice husk-activated carbon (RHAC) had good pore structure and oxygen-containing functional groups. The influences of contact time, initial concentration of Hg(II), adsorbent dosage, pH, and ionic strength on mercury ion removal were investigated. The Langmuir model was most suitable for the adsorption isotherm of RHAC, and its maximum adsorption capacity for Hg(II) was 55.87 mg/g. RHAC still had a high removal capacity for Hg(II) after five regeneration cycles. RHAC had excellent removal efficiency for mercury ion wastewater. At the same time, RH could be used as a nonpolluting and outstanding characteristic adsorbent material.

MnO2 flowery nanocomposites for efficient and fast removal of mercury(ii) from aqueous solution: a facile strategy and mechanistic interpretation

MnO2 flowery nanocomposites were explored as a novel and cost effective nanoadsorbent for the fast and efficient extraction of toxic inorganic contaminants from aqueous solution.

Data of preparation and characterization of activated carbon using two activant agents and mango seed as precursor material

The aim of this research is to prepare various carbonaceous materials with different textural, structural and chemical characteristics, using mango seed a rarely used residue for the preparation of activated carbons, as the precursor material. The mango seed was analyzed by TGA and SEM also methodological data about the preparation of activated carbons are provided. Four activated carbons were prepared using sulfuric acid (H₂SO₄) and calcium chloride (CaCl₂) as activating agents and were characterized by means of TGA, SEM/EDX, Boehm Titration, isotherm determination of N₂ adsorption-desorption at −196 °C and immersion calorimetry. Four carbons were obtained with superficial areas BET between 6 and 33 m² g⁻¹ and different chemical characteristics associated with the changes in the concentration of the activating agents. The activated carbons that were prepared with the highest activating agent concentrations, obtained better results in the amount of oxygenated surface groups, the total acidity and the amount of fixed carbon. The enthalpy of immersion in water was between 7 and 16 J g⁻¹.

Adsorptive removal of mercury from water by adsorbents derived from date pits

The current work presented here focuses on the remediation of mercury from water using modified low-cost materials. Modified date pits, low cost, minimal pretreatment steps and locally abundant agricultural waste materials were effectively employed as an adsorbent for remediating Hg2+ from aqueous media. Physical and chemical modification were developed such as thermal roasting (RDP), sulfur (SMRDP) and silane (SIMRDP) based modifications. Results showed that maximum adsorption by RDP was at pH 6, AC and both modifications was at pH 4. Furthermore, RDP has exothermic adsorption mechanism while AC, SMRDP, and SIMRDP have endothermic. All adsorbents except SIMRDP have spontaneous adsorption process. SEM analysis showed that the surface morphology of RDP was not significantly affected by different treatments while surface of AC was affected. The investigation for good adsorbents for Hg2+ uptake from different anthropogenic sources has been carried out by many investigators worldwide towards having a safe environment. In the current study, the highest Hg2+ adsorption of SMRDP was relatively high compared to other known adsorbents.

Gas-phase elemental mercury removal using ammonium chloride impregnated sargassum chars

In this article, pyrolyzed bio-chars derived from a kind of macroalgae, sargassum, were modified by ammonium chloride (NH4Cl) impregnation, and were applied to remove Hg0 from flue gas. The characteristics of sorbents were investigated by the Brunauer-Emmett-Teller, X-ray photoelectron spectroscopy, scanning electron microscopy and ultimate and proximate analysis. The key parameters (e.g. loading value, reaction temperature and concentration of O2, NO, SO2 and water vapor), kinetics analysis and reaction mechanism of Hg0 removal were investigated. The results show that increasing loading value, reaction temperature, O2 concentration and NO concentration enhance Hg0 removal. The increase in SO2 concentration or water vapor concentration has a dual effect on Hg0 removal. The C-Cl groups and C=O groups play an important role in the process of Hg0 removal. The Hg0 removal process of modified samples meets the pseudo-second-order kinetic model.

Investigation of mercury adsorption and cyclic mercury retention over MnOx/γ-Al2O3 sorbent

In this study mercury sorbent based on manganese oxides impregnated γ-alumina was synthesized. Mercury retention characteristics were investigated by mercury speciation and thermal desorption experiments. No gaseous mercuric oxide was observed in mercury speciation experiments with a mercury mass balance ratio of 89.11%. Maximum mercury desorption peak at 480 °C indicated that mercury was adsorbed in the form of mercuric oxide. Three cycles of mercury retention were tested with different thermal treatment in-between to evaluate the cyclic performance. Changes in surface phase and manganese chemistry before and after thermal treatment were characterized by XRD and XPS. Deterioration in mercury retention capacity was observed after thermal desorption at 500 °C, which was interpreted with reduced initial adsorption rate calculated by Pseudo-second order kinetic model. XPS studies suggested that atomic ratios of Mn⁴⁺/(Mn⁴⁺+Mn³⁺) decreased from 73.2% to 32.3% and 33.9% after thermal desorption in N₂ and air, respectively. The reduction of MnO₂ to Mn₂O₃ was irreversible thus the mercury retention capacity could not be restored by thermal desorption at high temperatures. Spent sorbents that were reactivated at 200 °C in air without thermal desorption at 500 °C possessed considerable cycling performance for mercury retention due to the preserved Mn⁴⁺.