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Pine cone bio-char was synthesized through slow pyrolysis at 500°C, characterized and used as an effective adsorbent in the removal of organic Methylene Blue (MB) dye and inorganic nickel metal (Ni(II) ions from aqueous phase. Batch adsorption kinetic study was carried out by varying solution pH, dye concentration, temperature, adsorbent dose and contact time. Kinetic and isotherm models indicates that the adsorption of both adsorbates onto pine cone bio-char were mainly by chemisorption. Langmuir maximum adsorption capability was found to be 106.4 and 117.7mg/g for Methylene Blue (MB) and nickel ions (NI(II) respectively. Thermodynamic parameters suggested that the adsorption was an endothermic and spontaneous. These results indicate the applicability of pine cone as a cheap precursor for the sustainable production of cost-effective and environmental friendly bio-char adsorbent.

A B S T R A C TEucalyptus bark (EB) materials-based bio-char adsorbent was synthesised and characterised using SEM-EDS, BET and CHN analyser. The adsorbent surface functional groups were determined by FT-IR analyser. Various textural characteristics such as BET surface area, pore size, bulk density, point of zero charge were also determined. The adsorption potential of these bio-char for the removal of cationic dye Methylene Blue (MB) from aqueous solution was studied. The effects of various temperature profiles on the production of EB biochar were studied and the most efficient temperature profile was identified at 500˚C. Batch adsorption kinetic study showed that the amount of dye adsorbed q t (mg/g) depends on various physicochemical process parameters such as initial solution pH, dye concentration, temperature, adsorbent dose, salt concentration and presence of SDS surfactant. It was found that the extent of MB dye adsorption by EB bio-char increased with the increase of initial dye concentration, contact time, temperature, SDS surfactant concentration and solution pH, but decreased with the increase of adsorbent dose and salt concentration. The optimum adsorption conditions were found at the initial dye concentration of 100 mg/L, initial solution pH of 11.3, adsorbent dose of 10 mg and solution temperature of 55˚C. Furthermore, pseudo-first-order, pseudo-second-order and intra-particle diffusion models were fitted to examine the adsorption kinetics and mechanism of adsorption. Equilibrium data were best represented by Langmuir isotherm model and gives a monolayer effective adsorption capacity of bio-char which is comparative to other adsorbents including commercial activated carbon. Thermodynamic parameters suggested that the adsorption was an endothermic, spontaneous and physical in nature. Furthermore, a single-stage batch adsorber design for the MB dye onto EB bio-char particles were presented based on the Langmuir isotherm model equation. These results indicated EB biomass as good and cheap precursor for the production of an effective and environmental friendly bio-char adsorbent.

Dyes are complex organic compounds which are used by various industries to colour their products. These dyes are purged from various industrial sources such as textile, cosmetic, paper, leather, rubber and printing industries. Wastewater effluents contain dyes which may cause potential hazards to the environment. Some of these dyes are toxic, carcinogenic and can cause skin and eye irritation. Therefore, many researchers have been studied the effectiveness of dyes removal from aqueous solution by different separation methods. Different separation techniques have been used for the treatment of dye-bearing wastewater such as adsorption, coagulation/flocculation, advanced oxidation technologies, ozonation, and membrane-filtration, aerobic and anaerobic degradation. All dye separation techniques have their own limitation in terms of design, operation efficiency and total cost. This review paper provides extensive literature information about dyes, its classification and toxicity together with various treatment methods into dye adsorption characteristics of several non-conventional cost effective sustainable adsorbents. The mechanism and the effects of various physio-chemical process parameters on dye adsorption are presented here.

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A practical continuous adsorption study in a packed-bed column was conducted by using two separate layers of kaolin and pine cone based biochar packed bed adsorbents for the removal of methylene blue (MB) dye from its aqueous solution. A series of column experiments were performed to determine the breakthrough curves (BTCs) by varying bed height (3-7 cm), inlet flow rate (13-17 ml/min) and initial dye concentration (50-150 mg/L). The Thomas, Yoon-Nelson, Bed Depth Service Time (BDST) and Dose response (DR) dynamic models were applied to column experimental data under various operational conditions to predict the column breakthrough curves (BTC) using both nonlinear regression and linear regression and to determine various characteristic parameters such as percentage removal of dye, breakthrough time, used bed length, mass transfer zone (MTZ) and dye adsorption density q that are useful for process design. The MB dye adsorption was found to be most favourable under low flow rate, high adsorbent bed height and high initial dye concentrations. The experimental column breakthrough data were in good agreement with the various dynamic models and the results of various model characteristic parameters could be used to scale up the process to an actual industrial column operation. Also, this column study revealed the feasibility of pine cone biochar and kaolin adsorbents as alternative sustainable adsorbents for dye-bearing wastewater treatment.

a b s t r a c tThis present study evaluates the adsorptive effectiveness of mixed pine cone biomass and kaolin clay adsorbents in removing methylene blue (MB) dye from its aqueous solution using a packedbed column adsorption experiment. A series of column experiments were performed to determine the breakthrough curves (BTCs) by varying bed height, inlet feed flow rate and initial MB dye inlet concentration and various characteristic parameters such as % removal of dye, initial breakthrough time, used bed length and unused bed length, mass transfer zone (MTZ) and dye adsorption density (q total ) were determined here. The adsorption of MB dye was found most favourable under low feed flow rate, high adsorbent bed height and high initial MB dye concentrations. Four kinetic column models, namely Thomas, Yoon-Nelson, Clarkand Bed Depth Service Time (BDST) were fitted against the experimental data to predict the column breakthrough curves (BTC) behaviour under different operational conditions. All models were found suitable in describing the dynamic behaviour of the column. The various adsorptive kinetic parameters such as rate constant, the adsorption capacity for Thomas model, the time for 50% breakthrough in Yoon-Nelson model, Clark constants, the service time for BDST model and unused bed are determined and critically analysed which are useful for designing the large-scale column operation. This continuous column study revealed the strong ability of mixed pine cone biomass and kaolin clay packed bed adsorbents to remove the dye and other pollutants and may be recognised as an alternative sustainable solution for dye-bearing wastewater treatment in industrial scale.