Low-cost Natural Adsorbent Research Articles

Adsorption and Removal Kinetics of Phosphonate from Water Using Natural Adsorbents

The removal of phosphonate from water was studied using some natural adsorbents. Potassium phosphonate is a fungicide used for the control of Phytophthora capsici, which is prevalent in black pepper (Piper nigrum L.). Batch adsorption kinetic experiments were conducted on the adsorption of phosphonate onto the adsorbents. The concentration of phosphonate was measured on a high-performance liquid chromatograph fitted with a conductivity detector. The percentage removal of phosphonate by powdered laterite stone (PLS) from water was 40.4%, within a residence time of 15 minutes. The mechanisms of the rate of adsorption were analyzed and compared using the pseudo-second-order, Elovich, and intraparticle diffusion models. The experimental data was found to correlate well with the pseudo-second-order kinetic model, indicating adsorption as a chemisorption process. A possible reaction in the phosphonate-PLS system also has been proposed. The PLS can be used as a low-cost natural adsorbent for phosphonate removal from water.

Fixed-bed column study for the removal of cadmium (II) and nickel (II) ions from aqueous solutions using peat and mollusk shells

The study was conducted to examine the effectiveness of 4.0–4.75 mm crushed shells and Sphagnum peat moss as low-cost natural adsorbent filter materials for the removal of cadmium and nickel ions from binary aqueous solutions. The effects of column depth and flow rate on effluent metal breakthrough, metal removal and pH were investigated as a function of throughput volume (TPV). Metal removal efficiencies and adsorption capacities for each of the columns were estimated to identify the better filter material and operational conditions for the treatment of cadmium and nickel. During the column testing, a flow rate of 1.5 mL/min (surface loading of 27.5 cm 3/cm 2 day) and bed depth of 15 cm were found to represent the better operational conditions, where 47.9% and 42.7% cadmium and nickel cumulative removals were obtained under these operational conditions, respectively. The results will be valuable in the development of a mixed-media adsorption system for the treatment of metal-rich wastewaters such as municipal landfill leachate.

Saw dust and neem bark as low-cost natural biosorbent for adsorptive removal of Zn(II) and Cd(II) ions from aqueous solutions

The ability of saw dust and neem bark as low-cost natural adsorbents were investigated for adsorptive removal of Zn(II) and Cd(II) ions from aqueous solutions. Various physico-chemical parameters such as pH, initial metal ion concentration, and adsorbent dosage level and equilibrium contact time were studied. The optimum pH for adsorption was found to be 5 for Zn(II) and 6 for Cd(II). Kinetics data were best described by pseudo-second-order model. Mass transfer coefficients were also determined for individual adsorbents for removal of Zn(II) and Cd(II) ions from aqueous solutions. The equilibrium adsorption data were fitted to Langmuir and Freundlich isotherm models for Zn(II) and Cd(II) adsorption respectively. The adsorption capacities (qmax) for individual metal ions in terms of monolayer adsorption were compared with the other reported values. The sorption energy calculated by using Dubinin–Radushkevich isotherm for different system indicated that the adsorption process is physical in nature. The thermodynamic equilibrium constant and the Gibbs free energy were determined for each system and results indicated the spontaneous nature of the adsorption process. FT-IR studies were carried out to understand the type of functional groups in saw dust and neem bark responsible for metal binding process.

Arsenic removal from real-life groundwater by adsorption on laterite soil

The adsorption characteristics of arsenic on laterite soil, a low-cost natural adsorbent, were studied in the laboratory scale using real-life sample. The studies were conducted by both batch and continuous mode. Laterite soil was found to be an efficient adsorbent for arsenic removal from the groundwater collected from arsenic affected area. The initial concentration of arsenic in the sample was 0.33 ppm. Under optimized conditions the laterite soil could remove up to 98% of total arsenic. The optimum adsorbent dose was 20 g/l and the equilibrium time was 30 min. Isotherm studies showed that the process is favorable and spontaneous. The kinetics showed that the removal of arsenic by laterite soil is a pseudo-second-order reaction. In the column study the flow rate was maintained at 1.49 m 3/(m 2 h). Using 10 cm column depth, the breakthrough and exhaust time found were 6.75 h and 19.0 h, respectively. Height of adsorption zone was 9.85 cm, the rate at which the adsorption zone was moving through the bed was 0.80 cm/h, and the percentage of the total column saturated at breakthrough was 47.12%. The value of adsorption rate coefficient ( K) and the adsorption capacity coefficient ( N) were 1.21 l/(mg h) and 69.22 mg/l, respectively. Aqueous NaOH (1 M) could regenerate the adsorbent, and the regenerated adsorbent showed higher efficiency.

Methylene blue biosorption from aqueous solutions by yellow passion fruit waste

The yellow passion fruit ( Passiflora edulis Sims. f. flavicarpa Degener) (YPFW) a powdered solid waste, was tested as biosorbent for the removal of a cationic dye, methylene blue (MB), from aqueous solutions. Adsorption of MB onto this low-cost natural adsorbent was studied by batch adsorption at 25 °C. The effects of shaking time, biosorbent dosage and pH on adsorption capacity were studied. In alkaline pH region the adsorption of MB was favorable. The contact time required to obtain the maximum adsorption was 48 h at 25 °C. Four kinetic models were tested, being the adsorption kinetics better fitted to pseudo-first order and ion exchange kinetic models. The ion exchange and pseudo-first order constant rates were 0.05594 and 0.05455 h −1, respectively. The equilibrium data were fitted to Langmuir, Freundlich, Sips and Redlich–Peterson isotherm models. Taking into account the analysis of the normal distribution of the residuals (difference of q measured − q model), the data were best fitted to Sips isotherm model. The maximum amount of MB adsorbed on YPFW biosorbent was 44.70 mg g −1.

Decolourization of Textile Effluent Using a Low Cost Natural Adsorbent Material

To evaluate their abilities to remove colour from textile-plant effluents, tests were run using several low cost natural adsorbent materials including vermiculite, sawdust, barbecue charcoal, maize stalks, sand, rice husks and peatmoss. With the exception of vermiculite, more than 50% of the colour was removed from the wastewater, with barbecue charcoal and rice husks showing the best adsorptive qualities (67% and 65% respectively). Under simulated industrial conditions on a laboratory scale a fixed-bed reactor was used to investigate the adsorption capacity of barbecue charcoal with respect to colour removal. An average of 28% of colour was removed at a hydraulic retention time (HRT) of 1.6 h over a period of 25 days. The effect of pH on the adsorptive capacity with respect to colour removal and represents a relatively cheap adsorbent material compared to conventionally used granular activated carbon.