Influence of carbon dioxide partial pressure and fluidization velocity on activated carbons prepared from scrap car tyre in a fluidized bed

Synthesis and Characterisation of Activated Carbon Obtained from Marula (Sclerocarya birrea) Nutshell

Globally, a ninth of people use polluted water sources because an estimated 300–400 Mt of waste and 90% of sewage are discharged into water bodies from industries and developing countries, respectively. The utilisation of indigenous fruit pits in producing novel adsorbents will greatly benefit in wastewater treatment. In most underdeveloped countries, activated carbon (AC) is imported at a high cost. The study was aimed at synthesising and characterisation of AC obtained from Marula nutshell. Carbonization of organic matter from Marula nutshell was carried out at 200°C, 400°C, 500°C, and 600°C. Sulphuric (H2SO4) and phosphoric (H3PO4) acids were used as activating agents at concentrations of 20–60% ( $v/v$ ). Physicochemical characteristics of the AC, such as bulk density, moisture, ash, pH, and iodine number, were analyzed using standard methods. Functional groups and total carbon content were determined using the FTIR spectroscopy and Nitrogen Carbon Sulphur (NCS) analyzer, respectively. The values of carbon yield and total carbon in activated samples with H2SO4 and H3PO4 were 32.2–93.2%, 26.9–95.8%, and 46–79%, 20.8–69.8%, respectively. The pH, ash, moisture, and bulk density of activated high carbon samples with H2SO4 ranged from 2.4–6.1, 0.65–3.49%, 1.3–8.4%, and 0.42–0.62 gcm−3, respectively. Activated high carbon samples with H3PO4 had 2.7–3.2, 11.3–29.8%, 4.7–14.6%, and 0.39–0.54 gcm−3 pH, ash, moisture, and bulk density, respectively. The synthesised AC samples with 40% H3PO4 at 500°C had the highest iodine value of 1075.7 mg/g. FTIR results showed the presence of aliphatic carboxylic acid salt, inorganic nitrate (NO3−), and phosphate groups in the synthesised AC and were not significantly different ( $p<0.05$ ) from commercial AC. The untreated Marula nutshell had some aliphatic hydrocarbon (alkanes), inorganic phosphate ( ${\text{PO}}_4^{3-}$ ), aliphatic ester (–COO), and aliphatic carboxylic acid salt (–C(=O)O–) groups. A novel adsorbent, AC was produced from Marula nutshell with the potential to be used in water treatment.

Adsorptive removal of microcystin-LR from surface and wastewater using tyre-based powdered activated carbon: Kinetics and isotherms

Microcystin LR (MC-LR) is a highly toxic compound and it is known for its adverse health effect on both humans and animals. Due to the ineffectiveness of conventional water treatments methods, for the past decades, researchers have been developing cost-effective ways of removing MC-LR from water bodies. This study reports the application of powdered activated carbon (PAC) obtained from the waste tyre for the removal of MC-LR. The choice of the adsorbent was chosen due to its attractive properties. The prepared tyre-based PAC was found to have the large surface area (1111 m² g^-1). The detection of MC-LR was achieved using high performance liquid chromatography (HPLC) coupled with a PDA detector. The experimental parameters (such as optimum pH, dosage and contact time) affecting the removal of MC-LR using tyre based-powdered activated carbon were optimized using response surface methodology (RSM). Maximum removal of MC-LR was achieved under the following optimum conditions; sample pH 4, carbon dosage concentration 10,000 mg L^-1 and contact time of 34 min. Under optimum conditions, kinetic studies and adsorption isotherms reflected better fit for pseudo-second-order rate and Langmuir isotherm model, respectively. The optimized method was applied for the removal of MC-LR in wastewater sample. The effluent and influent sample contained initial concentrations ranging from 0.52 to 8.54 μg L^-1 and the removal efficiency was 100%.

Processing methods, characteristics and adsorption behavior of tire derived carbons: a review

The remarkable increase in the number of vehicles worldwide; and the lack of both technical and economical mechanisms of disposal make waste tires to be a serious source of pollution. One potential recycling process is pyrolysis followed by chemical activation process to produce porous activated carbons. Many researchers have recently proved the capability of such carbons as adsorbents to remove various types of pollutants including organic and inorganic species. This review attempts to compile relevant knowledge about the production methods of carbon from waste rubber tires. The effects of various process parameters including temperature and heating rate, on the pyrolysis stage; activation temperature and time, activation agent and activating gas are reviewed. This review highlights the use of waste-tires derived carbon to remove various types of pollutants like heavy metals, dye, pesticides and others from aqueous media.

Preparation and characterization of activated carbon from the char produced in the thermolysis of granulated scrap tyres

The char produced in the thermolysis of granulated scrap tyres has few market outlets, reducing the economic viability of the thermolytic process. This paper reports the potential of this char as a low-cost precursor of porous carbons. The tyre-derived char was demineralized in either alkaline or acidic media to reduce its ash, zinc, sulfur, and silica contents. The lowest impurity content was achieved with an HNO3/H2O treatment. The resulting demineralized char was then subjected to activation by KOH or CO2. The Brunauer-Emmett-Teller (BET)-specific surface area of the activated carbon produced by the KOH treatment was 242 m2/g, whereas that of the CO2-activated carbon was 720 m2/g. The textural properties of the latter product were similar to those of some commercial activated carbons. The use of tyre-derived char as a precursor of porous carbons could render the thermolytic treatment of scrap tyres more economically attractive.

IMPLICATIONS

Char produced in thermolysis of granulated scrap tyres has a few market outlets; in this paper an alternative for its use is presented. The char was converted into activated carbon with textural properties similar to those of some commercial activated carbons. This process could render the thermolytic treatment of scrap tyres more economically attractive.

Chromium removal from water by activated carbon developed from waste rubber tires

Because of the continuous production of large amount of waste tires, the disposal of waste tires represents a major environmental issue throughout the world. This paper reports the utilization of waste tires (hard-to-dispose waste) as a precursor in the production of activated carbons (pollution-cleaning adsorbent). In the preparation of activated carbon (AC), waste rubber tire (WRT) was thermally treated and activated. The tire-derived activated carbon was characterized by means of scanning electron microscope, energy-dispersive X-ray spectroscopy, FTIR spectrophotometer, and X-ray diffraction. In the IR spectrum, a number of bands centred at about 3409, 2350, 1710, 1650, and 1300-1000 cm(-1) prove the present of hydroxyl and carboxyl groups on the surface of AC in addition to C═C double bonds. The developed AC was tested and evaluated as potential adsorbent removal of chromium (III). Experimental parameters, such as contact time, initial concentration, adsorbent dosage and pH were optimized. A rapid uptake of chromium ions was observed and the equilibrium is achieved in 1 h. It was also found that the adsorption process is pH dependent. This work adds to the global discussion of the cost-effective utilization of waste rubber tires for waste water treatment.