Use of an activated carbon from antibiotic waste for the removal of Hg(II) from aqueous solution

Porous carbon has been prepared from waste antibiotic material by a chemical activation method using K(2)CO(3) as an activating reagent. Carbon was studied systematically by the adsorption of nitrogen and iodine. It was found that the process parameters such as activation temperature and activation time are crucial for preparing high-quality activated carbon. The proper choice of the preparation conditions allows to produce microporous activated carbon with a micropore volume up to 0.492 cm(3)/g and a BET surface area of 1260 m(2)/g. Adsorption of mercury(II) from an aqueous solution on antibiotic carbon was investigated under the varying conditions of agitation time, metal ion concentration and pH. The adsorption capacity of the carbon is 129 mg/g.     

Removal of Pb(II) ions from aqueous solution using activated tea waste: Adsorption on a fixed-bed column

An inexpensive and effective adsorbent was developed from waste tea leaves for the dynamic uptake of Pb(II). Characterization of the adsorbents showed a clear change between physico-chemical properties of activated tea waste and simply tea waste. The purpose of this work was to evaluate the potential of activated tea waste in continuous flow removal of Pb(II) ions from synthetic aqueous effluents. The performance of the system was evaluated to assess the effect of various process variables, viz., of bed height, hydraulic loading rate and initial feed concentration on breakthrough time and adsorption capacity. The shape of the breakthrough curves was determined for the adsorption of Pb(II) by varying different operating parameters like hydraulic loading rate (2.3–9.17 m³/h m²), bed height (0.3–0.5 m) and feed concentration (2–10 mg/l). An attempt has also been made to model the data generated from column studies using the empirical relationship based on the Bohart–Adams model. There was an acceptable degree of agreement between the data for breakthrough time calculated from the Bohart–Adams model and the present experimental study with average absolute deviation of less than 5.0%. The activated tea waste in this study showed very good promise as compared with the other adsorbents available in the literature. The adsorbent could be suitable for repeated use (for more than four cycles) without noticeable loss of capacity.     

Removal of o-nitrophenol from water by electrochemical degradation using a lead oxide/titanium modified electrode

This study examined o-nitrophenol removal from aqueous solutions by electrochemical oxidation employing a modified electrode. The modified electrode was produced by electrodepositing lead oxide onto a titanium substrate. Following electrochemical oxidation of o-nitrophenol-containing solutions, the remaining o-nitrophenol concentration and chemical oxygen demand (COD) values were determined. The optimum parameters were current density of 40 mA cm(-2), pH of 2.47, 60 min of electrolysis time, 4 g L(-1) NaCl electrolyte solution and temperature of 30 degrees C. Under these optimum conditions of electrochemical degradation using a lead oxide/titanium modified electrode complete removal of o-nitrophenol and COD was achieved.     

Exploitation of Trichoderma harzianum mycelial waste for the removal of rhodamine 6G from aqueous solution

The harvested mycelial waste of Trichoderma harzianum was used as an adsorbent for the removal of rhodamine 6G and was studied in batch mode. The effects of agitation time and initial dye concentration, adsorbent dosage and pH were examined. The study revealed that the amount of dye adsorbed (mgg(-1)) increased with increase in agitation time and reached equilibrium after 120 min, for dye concentrations of 10-50 mg L(-1). The adsorbent dosage of 1.0 g/50 mL and pH of 8.0 were found to be optimum for maximum dye removal. The batch mode adsorption data followed both the Langmuir and Freundlich isotherms. The pseudo first- and second-order rate kinetics were applied to the adsorbent system. The adsorption kinetics of rhodamine 6G showed that the pseudo-second-order kinetic model provided the best correlation of the equilibrium data. The study implies that it is possible to develop a dye removal system by using T. harzianum biomass, which occurs as sludge in waste stream of fermentation industries.     

Loofa egyptiaca as a novel adsorbent for removal of direct blue dye from aqueous solution

In this paper, Loofa egyptiaca (LE), an agricultural plant cultivated in Egypt, was used to prepare low-cost activated carbon (LE_C1 and LE_C2) adsorbents. The adsorbents (LE, LE_C1 and LE_C2) were evaluated for their ability to remove direct blue 106 dye from aqueous solutions. Batch mode experiments were conducted using various parameters such as pH, contact time, dye concentration and adsorbent concentration. The surface chemistry of LE, LE_C1 and LE_C2 was analyzed by scanning electron microscopy (SEM). The experimental data were examined using Langmuir, Freundlich, Temkin and Harkins–Jura isotherms. The results showed that the adsorption of direct blue 106 was maximal at the lowest value of pH (pH = 2). Removal efficiency was increased with an increase in dye concentration and a decrease in amount of adsorbent. Maximum adsorption capacity was found to be 57.14, 63.3 and 73.53 mg/g for LE, LE_C1 and LE_C2 respectively. Kinetics were also investigated using pseudo-first-order, pseudo-second-order and intra-particle diffusion models. The experimental data fitted very well with the pseudo-first-order and pseudo-second-order kinetic models. The results indicate that LE, LE_C1 and LE_C2 could be employed as adsorbents for the removal of direct blue dye from aqueous solutions.     

Biosorption of Cu and Zn from aqueous solutions by dried marine green macroalga Chaetomorpha linum

The biosorption of the heavy metals Cu²⁺ and Zn²⁺ by dried marine green macroalga (Chaetomorpha linum) was investigated. The biosorption capacities of the dried alga for copper and zinc were studied at different solution pH values (2–6), different algal particle sizes (100–800 μm) and different initial metal solution concentrations (0.5–10 mM). An optimum pH value of 5 was found suitable for both metal ions biosorption for both metal ions. At the optimum particle size (100–315 μm), biosorbent dosage (20 g/l) and initial solution pH (pH 5), the dried alga produced maximum copper and zinc uptakes values (q_max) of 1.46 and 1.97 mmol/g respectively (according to the Langmuir model). The kinetic data obtained at different initial metal concentrations indicated that the biosorption rate was fast and most of the process was completed within 120 min. This study illustrated an alternative technique for the management of unwanted biological materials using processed algal material. C. linum is one of the fast-growing marine algae in the lake of Tunis and could be utilized as a biosorbent for the treatment of Cu²⁺ and Zn²⁺ contaminated wastewater streams.