Determination of the point of zero charge of pineapple (Ananas comosus L.) peel and its application as copper adsorbent

Objective: To determine the optimum pH at which the pineapple peel can adsorb the greatest amount of copper. Design/methodology/approach: Sorbent material. The size of the pineapple peel was reduced to 0.250 mm; it was chemically modified with 0.2 M NaOH and 0.2 M CaCl2. Point of zero charge (PZC). Six solutions were prepared with 0.5 g of sorbent in an aqueous medium (with a 3-8 pH range), they were stirred at 225 rpm for 48 h. The derivative method was used to plot the initial pH versus final pH, in order to determine the PZC. Copper adsorption. CuSO4 solutions were prepared in 2, 4, 6, 8 10 mg/L concentrations; 0.1 g of pineapple biomass was added adjusting the pH to 5. The solutions had a contact time of 0 to 24 h. Results: The pineapple peel had a 5.0 point of zero charge (PZC) value, which indicates that pH values higher than the PZC are required to obtain an adsorbent with a negatively charged surface and favor the copper adsorption. A 50% copper removal was obtained in all concentrations after a 1 h contact time. Limitations on study/implications: This research had no limitations. Findings/conclusions: The point of zero charge is a reliable parameter that allows the adsorption process to take place and provides a greater certainty to the metal adsorption process. Meanwhile, pineapple peel can be used as an adsorbent material, consequently reducing its accumulation in open dumps.

INVESTIGATION OF THE THERMODYNAMIC CHARACTERISTICS OF THE EXTRACTION OF COPPER IONS FROM AQUEOUS SOLUTIONS USING ACTIVATED CARBON

Изучение термодинамических и кинетических характеристик позволяет более эффек- тивно использовать углеродные адсорбенты в технологических процессах, чем поддерживается тех- нология их использования на оптимальном уровне. В работе изучалась адсорбционная активность углеродных нанопористых материалов, рассчитывались кинетические характеристики процесса ад- сорбции, термодинамические характеристики (энергия Гиббса, энтальпия, константа адсорбции) адсорбции ионов меди на активных углях, полученных на установках (модульная пиролизная реторт- ная установка) и УВП (углевыжигательная печь). Установлено, что процесс идёт самопроизвольно, характер адсорбционного взаимодействия экзотермический. Адсорбционные равновесие достигается меньше чем за 15 мин. The study of thermodynamic and kinetic characteristics allows more efficient use of carbon adsorbents in technological processes. Thus, keeping their use at an optimal level. The adsorption activity of carbon nanoporous materials was studied, the kinetic characteristics of the adsorption process, thermodynamic characteristics (Gibbs energy, enthalpy, adsorption constant) of copper adsorption on activated carbons obtained at MPRP and CK installations were calculated in this work. It was found that the process is spontaneous (G <0). The nature of the adsorption behavior is exothermic. Adsorption equilibrium is achieved in less than 15 minutes.

Innovative method for encapsulating highly pigmented biomass from Aspergillus nidulans mutant for copper ions removal and recovery

Biosorption has been considered a promising technology for the treatment of industrial effluents containing heavy metals. However, the development of a cost-effective technique for biomass immobilization is essential for successful application of biosorption in industrial processes. In this study, a new method of reversible encapsulation of the highly pigmented biomass from Aspergillus nidulans mutant using semipermeable cellulose membrane was developed and the efficiency of the encapsulated biosorbent in the removal and recovery of copper ions was evaluated. Data analysis showed that the pseudo-second-order model better described copper adsorption by encapsulated biosorbent and a good correlation (r2 > 0.96) to the Langmuir isotherm was obtained. The maximum biosorption capacities for the encapsulated biosorbents were higher (333.5 and 116.1 mg g-1 for EB10 and EB30, respectively) than that for free biomass (92.0 mg g-1). SEM-EDXS and FT-IR analysis revealed that several functional groups on fungal biomass were involved in copper adsorption through ion-exchange mechanism. Sorption/desorption experiments showed that the metal recovery efficiency by encapsulated biosorbent remained constant at approximately 70% during five biosorption/desorption cycles. Therefore, this study demonstrated that the new encapsulation method of the fungal biomass using a semipermeable cellulose membrane is efficient for heavy metal ion removal and recovery from aqueous solutions in multiple adsorption-desorption cycles. In addition, this reversible encapsulation method has great potential for application in the treatment of heavy metal contaminated industrial effluents due to its low cost, the possibility of recovering adsorbed ions and the reuse of biosorbent in consecutive biosorption/desorption cycles with high efficiency of metal removal and recovery.

Removal of Toxic Copper Ion from Aqueous Media by Adsorption on Fly Ash-Derived Zeolites: Kinetic and Equilibrium Studies

This study investigated the adsorption capacity of one material based on the treatment of fly ash with sodium hydroxide as a novel adsorbent for toxic Cu2+ ion removal from aqueous media. The adsorbent was obtained through direct activation of fly ash with 2M NaOH at 90 °C and 6 h of contact time. The adsorbent was characterized by recognized techniques for solid samples. The influence of adsorption parameters such as adsorbent dose, copper initial concentration and contact time was analyzed in order to establish the best adsorption conditions. The results revealed that the Langmuir model fitted with the copper adsorption data. The maximum copper adsorption capacity was 53.5 mg/g. The adsorption process followed the pseudo-second-order kinetic model. The results indicated that the mechanism of adsorption was chemisorption. The results also showed the copper ion removal efficiencies of the synthesized adsorbents. The proposed procedure is an innovative and economical method, which can be used for toxicity reduction by capitalizing on abundant solid waste and treatment wastewater.

Preparation of Bamboo-Based Hierarchical Porous Carbon Modulated by FeCl3 towards Efficient Copper Adsorption

Using bamboo powder biochar as raw material, high-quality meso/microporous controlled hierarchical porous carbon was prepared—through the catalysis of Fe3+ ions loading, in addition to a chemical activation method—and then used to adsorb copper ions in an aqueous solution. The preparation process mainly included two steps: load-alkali leaching and chemical activation. The porosity characteristics (specific surface area and mesopore ratio) were controlled by changing the K2CO3 impregnation ratio, activation temperature, and Fe3+ ions loading during the activation process. Additionally, three FBPC samples with different pore structures and characteristics were studied for copper adsorption. The results indicate that the adsorption performance of the bamboo powder biochar FBPC material was greatly affected by the meso/micropore ratio. FBPC 2.5-900-2%, impregnated at a K2CO3: biochar ratio of 2.5 and a Fe3+: biochar mass ratio of 2%, and activated at 900 °C for 2 h in N2 atmosphere, has a very high specific surface area of 1996 m2 g−1 with a 58.1% mesoporous ratio. Moreover, it exhibits an excellent adsorption capacity of 256 mg g−1 and rapid adsorption kinetics for copper ions. The experimental results show that it is feasible to control the hierarchical pore structure of bamboo biochar-derived carbons as a high-performance adsorbent to remove copper ions from water.