The coagulation–flocculation–sedimentation process is widely used for removal of suspended solids and water turbidity reduction. The most common coagulants used to conduct this process are aluminum sulfate and ferric sulfate. In this paper, the use of Aloe vera as a natural-based coagulant for drinking water treatment was tested. The bio-coagulant was used in two different forms: powder as well as liquid; the latter was extracted with distilled water used as a solvent. The obtained results showed that the use of the natural coagulant (Aloe vera) in both powder (AV-Powder) and liquid (AV-H₂O) forms reduced the water turbidity at natural pH by 28.23% and 87.84%, respectively. Moreover, it was found that the use of the two previous forms of bio-coagulant for drinking water treatment had no significant influence on the following three parameters: pH, alkalinity, and hardness. The study of the effect of pH on the process performance using Aloe vera as a bio-coagulant demonstrated that the maximum turbidity removal efficiency accounted for 53.53% and 88.23% using AV-Powder and AV-H₂O, respectively, at optimal pH 6.

Pine cones are a widely available and abundant natural resource in Algeria, and they are rich in active molecules. This study investigated the valorization of Pine cones as a natural and abundant bio-coagulant in raw form (powder) and extract form. The active components of the Pine cones were extracted using two solvents, distilled water (DW) and NaCl, to obtain coagulants (proteins, polyphenols, and carbohydrates) for the treatment and improvement of industrial water quality parameters (discharge from a processing plant and tomato production) and an adsorbent (residue extract, RE). The recovered bio-coagulant was used to remove turbidity, chemical oxygen demand (COD), and zeta potential. The formed adsorbent was used to remove crystal violet (CV). Coagulation-flocculation experiments were carried out in a jar test to evaluate the performance of the coagulant in powder and extract form. The use of pine cone powder (PCP), extract using NaCl (PC-NaCl), and extract using DW (PC-DW) resulted in turbidity reductions of 96%, 94%, and 98%, respectively. For the residue recovered after extraction, a CV removal percentage of 99.9% was achieved at the optimal conditions of pH 10, CV concentration of 20 mg/L, adsorbent dose of 20 mg/L, and contact time of 120 min, as determined using the Box–Behnken design (BBD). Furthermore, all the effects were significant in the process of the CV phase adsorption on the bio-adsorbent. The model designed for optimal design fit the experimental data well, with a coefficient of determination, R², of 0.965 and an Adj-R² of 0.926. The p-value of this model was 0.000, which indicated that the model was very significant. This confirmed the effectiveness of the bio-adsorbent in removing dyes from water.

The present work aims to assess the effectiveness and efficiency of orange peels as a low-cost biosorbent for removing Cr(VI) from an aqueous solution by the biosorbent process. The orange peels as adsorbent was characterized using different methods, such as FTIR, pH_pzc, equilibrium pH, TGA, XRD, SEM, and (BET). The tests were conducted in the batch mode, and the effects of different parameters, such as the pH, dosage of the bioadsorbent, influent Cr(VI), and time, on the biosorption of Cr(VI) were investigated. The adsorption kinetics proved that a contact time of 90 min resulted in the highest (approximately 97.8%) Cr(VI) removal, with an adsorption capacity of 4.96 mg/g. Moreover, the increase in the biosorbent dosage (from 1 to 10 g/L) resulted in the enhancement in the Cr(VI) removal effectiveness. Moreover, the pH of the solution also affected significantly the effectiveness of the removal. The tests were conducted under acidic pH solution conditions, and the prediction of the pH value at a zero charge (pH _pzc) was confirmed experimentally. Furthermore, the results from the batch-mode assays were successfully tested by an experimental design (full factorial design). The biosorption of Cr(VI) on orange peels occurred mostly according to the pseudo-second-order kinetic model and the uptake of Cr(VI) was satisfactorily described by the Langmuir model.

The present work sheds light on the potentiality of proteins extracted from oak (Quercus robur) leaves to treat both drinking water and industrial oily wastewater. The work was structured in three steps: firstly, oak leaves in powder form were analyzed by FTIR, XRD and SEM, thus showing the presence of proteins acting as bio-coagulants; secondly, an experimental design was conducted. According to the design of experiences based on fractional design (2⁸⁻⁴), the highest protein concentration (4.895 mg/g) was obtained for the following operating parameters: no filtration, pH of 12, temperature of 20 °C, stirring speed of 300 rpm, stirring time of 60 min, maceration time of 4 h, centrifugation speed of 400 rpm, centrifugation time of 10 min. Finally, a jar test apparatus was used to study the effects of proteins from oak leaves on the characteristics of both drinking water and industrial oily wastewater. In drinking water, the turbidity was reduced from 15.7 to 4.82 NTU when 0.098 mg/L of oak leaves protein was added, thus satisfying the requirements of the national drinking water standards; whereas, in industrial oily wastewater turbidity, total suspended solids, chemical oxygen demand and organic matter were reduced by 96.87, 89.86, 96.39 and 46.28%, respectively, when 0.538 mg/L of oak leaves protein was added. This study opens new perspectives related to the research and development of organic coagulants applicable to industrial wastewater treatment.

The aim of this research was to valorize waste (sludge) from a drinking water treatment plant as a coagulant in the removal of dyes (methylene blue and crystal violet) from water and to prevent environmental issues associated with sludge storage. To accomplish this purpose, the response surface methodology based on a central composite design with five levels was implemented. In order to enhance the efficacy of the coagulation–flocculation process, three key operational variables were considered for optimization: the pH, coagulant dosage (mg/L), and initial dye concentration (mg/L). To achieve this, a quadratic polynomial model was established. According to the mathematical model that has been developed, it is predicted that the highest efficiency for removing dyes is 94.44%. This maximum effectiveness is reached when the pH is adjusted to 12.04, the coagulant dose is set at 87.044 mg/L, and the dye concentration of MB is maintained at 2.955 mg/L. Conversely, the best dye removal of CV was attained at 100% under the following conditions: pH = 12.045, a coagulant dosage of 2.955 mg/L, and a dye concentration of 2.955 mg/L. The R2 (98.44% and 95.80% for MB and CV, respectively) validated both models. In this work, the coagulant was characterized by the surface charge, FTIR, BET, and SEM analysis.

The present study concerns the process of chemical activation of agricultural waste, namely orange peels, to remove copper ions from aqueous solutions. In fact the use of orange peels without any pretreatment leads at the most a copper retention percentage of the order of 75%, whereas percentages over 99% could be achieved by means of chemical activations with sulphuric acid, caustic soda, methanol and acetic anhydride. A parametric study was also included, investigating the influence of the pH, initial concentrations of metal and the type of activation on the copper retention onto the orange peels. The results showed that saturation was reached after 10 and 5 min, for the cases of no pretreatment and the chemical activation of the orange peels, respectively. The pH study indicated that a value between 4 and 6 seemed to be the most adequate. The results did also show that the copper initial concentration value did have an influence on the retention capacity for the natural solid support. The sorption kinetic study showed that the process could be considered of a pseudo-second order, whereas the obtained equilibrium data were best fitted to the Freundlich model.