Statistical Modeling and Kinetic Studies on the Adsorption of Reactive Red 2 by a Low-Cost Adsorbent: Grape Waste-Based Activated Carbon Using Sulfuric Acid Activator-Assisted Thermal Activation

The efficiency of activated carbon produced from grape waste as a low-cost, nontoxic, and available adsorbent to remove Reactive Red 2 from aqueous solution has been investigated. The prepared activated carbon has been characterized by FTIR, SEM, and BET. The results of characterization indicate the successful conversion of grape waste into mesoporous AC with desirable surface area consist of different functional groups. The results of statistical modeling displayed high R 2 value of 0.97% for dye removal that shows the developed model has acceptable accuracy. The effect of independent variables indicated that the highest adsorption (96.83%) obtained at pH 3, adsorbent dosage of 12.25 g/L, and initial dye concentration of 100 mg/L when the adsorption time was 90 min. The results of isotherms modeling showed that the data fit well with the Langmuir (type II). The kinetic studies using pseudofirst-order and pseudosecond-order models pointed out that the type (I) of pseudosecond-order kinetic model provided the best fit to the adsorption data. Parameters of thermodynamics including Gibbs energy ( Δ G ° ) and k o were calculated. The values of Δ G ° indicated that the dye adsorption of RR2 is spontaneous. The agricultural wastes due to special points such as low-cost, availability, and high ability to produce an adsorbent with high efficiency to remove dye can be proposed for water and wastewater treatment.

Modern biotechnology in optimizing plant waste utilization

The study aimed to develop a modern, cheap, and environmentally safe technology for the disposal of plant waste, with the participation of the most active microorganisms-destructors.The microorganisms’ ability to help transform plant waste into viable, fertile soil was extensively studied. We selected strains of micromycetes Penicillium roseopurpureum, Trichoderma hamatum, T. koningii, Alternaria alternata, and bacteria of the genus Cytophaga, which are characterized by high growth rate and the absence of phytotoxicity. To accelerate microorganism development, we used silicon-containing mineral analcime, which contained immobilized spores of micromycetes and bacterial cells’ suspensions. Modified analcime was added to the waste in a ratio of 10 : 1. The plant remains prepared in this method were analyzed under conditions of both model and vegetation experiments.An evidence for the expediency of using the silicon-containing mineral analcime as a starting substrate for immobilization of spores and suspension of bacterial cells in the culture fluid was provided. The microorganisms involved in the experiment showed a positive result in transforming plant waste during the 30-day observation period. The highest destructive activity against apple and grape waste is characteristic for the T. hamatum strain, for beet waste – P. roseopurpureum. The species-specificity of these destructive microorganisms on plant growth processes was proved. The maximum growth of corn sprouts in apple waste was detected by inoculation with T. koningii spores, grape waste – T. hamatum, and beet waste – a mixture of micromycetes with a Cytophaga sp. suspension. The optimal duration of plant waste transformation using analcime, inoculated with microorganisms, is 20–30 days. In the indoor farming conditions, the standard for utilizing the modified vegetable waste placement was 10 % of the total volume of a substrate during the preparation of soil mixes.The environmental safety of plant waste after their destruction was confirmed. The presence of a silicon-containing mineral in the mixture leads to increased growth and plant development, optimization of the agrophysical, agrochemical, and biological parameters of the soil, reducing soil fatigue, and increasing fertility.

Food Waste Materials as Low-Cost Adsorbents for the Removal of Volatile Organic Compounds from Wastewater

The aim of this work was to study the potential of food waste materials (banana peel, potato peel, apple peel, lemon peel, coffee waste, decaf coffee waste, grape waste, and carob peel) as low-cost adsorbents for the removal of aliphatic and aromatic volatile organic compounds (VOCs) from wastewater. The ability of examined food waste materials to adsorb VOCs from synthetic multi-component standard solutions was evaluated and the examined food waste materials showed high removal efficiency. Performances of coffee waste, grape waste, and lemon peel were detailed by using Trichloroethylene and p-Xylene in mono-component standard solutions. The adsorption capacity of the three selected food wastes was determined by using linear Langmuir and Freundlich isotherm models. Two errors functions, average percentage error (APE) and the chi-square test (χ2), were used for isotherm optimization prediction. Freundlich isotherm well described the adsorption of VOCs on the considered materials. According to the obtained results, a multilayer, physical, and cooperative adsorption process was hypothesized, particularly evident when the VOCs’ concentrations are high. This was confirmed by the high adsorption efficiency percentages (E% > 80%) of VOCs from a real polluted matrix (urban solid waste leachate), containing high concentrations of total organic content.