Olive oil industry produces a large quantity of solid effluent (olive pomace OP) which can be used to get an economic profit. At the same time, crystal violet has been stated as a recalcitrant dye that perseveres in environment for extended time and bearings noxious influences in environment. In this work, olive pomace (OP) was treated by sodium hexametaphosphate (SHMP) and used as a low cost and eco-friendly biosorbent (SHMP-OP) for the removal of crystal violet (CV) from aqueous solutions. The prepared adsorbent characterised thru infrared spectroscopy (FT-IR), X-ray diffraction analysis (XRD) scanning electron microscope (SEM), energy dispersive X-ray analysis (EDX) and zero-point charge (pH_zpc). In the batch adsorption process, the effect of different factors like pH, adsorbent amount, initial dye concentration, temperature and contact time, on the removal of CV dye from aqueous solutions using SHMP-OP was examined. The results showed that maximum dye adsorption was found at pH 7 after equilibrium contact time of 50 min with a biosorbent dosage of 120 mg at temperature of 25°C. Langmuir and Freundlich isotherms were applied for the interpretation of experimental data. The isotherm studies showed that Langmuir was found to be best fitted with 271.003 mg/g maximum adsorption capacity. Also, successful desorption study using 0.5 mol/L of HCl has greatly promoted the spent adsorbent to be further used up to four consequent adsorption/desorption cycles. These results revealed that SHMP-OP is effective, eco-friendly and low-cost biomaterial for CV removal from aqueous media.

In this work, olive pomace, a lignocellulosic solid residue generated in olive oil production was chemically treated using sodium hexametaphosphate (SHMP) and utilised as an effective adsorbent (SHMP-OP) for removing anionic Congo red dye (CR) from aqueous solutions. Characterisation studies were undertaken on the prepared adsorbent using Fourier-transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray (EDX) and zero-point charge (pH_zpc). The zero-point charge was found to be 5.4. The FTIR findings showed that the surface of the prepared adsorbent contains mainly (–OH, C=O, and –NH) functional groups which are mainly responsible for the adsorption of CR dye. The SEM analyses for the prepared adsorbent showed a number of pores, highlighting its potential adsorption capacity. In batch method, the influence of different parameters as: initial pH, adsorbent dose, initial concentration of adsorbate, temperature, contact time, ionic strength, and presence of surfactant on the percentage removal of studied dye from aqueous media using SHMP-OP was investigated. The outcomes displayed that highest rate of adsorptive removal process for CR dye was found at pH 4 after 60 min equilibration time with 200 mg of SHMP-OP dose. Freundlich and Langmuir models were applied for the clarification of experimental data. Langmuir model showed that the maximum adsorption capacity equal 90.58 mg/g. Also, 0.08 mol/L of NaOH was used for successful regeneration study. The CR adsorption mechanism mainly involved electrostatic interaction and hydrogen bonding. Compared with some other adsorbents, SHMP-OP showed better removal efficiency of CR dye, suggesting possible and beneficial use of olive pomace waste residues to effectively decontaminate CR-contaminated wastewater. These obtained results showed that SHMP-OP is an effective, eco-friendly, and a low-cost adsorbent which can be used for the adsorptive removal of CR dye from aqueous solution.

The simultaneous generation of hydrogen fuel and wastewater remediation via electrocatalytic urea oxidation has emerged as a promising approach for sustainable energy and environmental solutions. However, the practical application of this process is hindered by the limited active sites and high charge-transfer resistance of conventional anode materials. In this work, we introduce a novel CoP@P, N-CNTs/NF electrocatalyst, fabricated through a facile one-step thermal annealing technique. Comprehensive characterizations confirm the successful integration of CoP nanoparticles and phosphorus/nitrogen co-doped carbon nanotubes (P, N-CNTs) onto nickel foam, yielding a unique hierarchical structure that offers abundant active sites and accelerated electron transport. As a result, the CoP@P, N-CNTs/NF electrode achieves outstanding urea oxidation reaction (UOR) performance, delivering current densities of 158.5 mA cm⁻² at 1.5 V and 232.95 mA cm⁻² at 1.6 V versus RHE, along with exceptional operational stability exceeding 50 h with negligible performance loss. This innovative, multi-element-doped electrode design marks a significant advancement in the field, enabling highly efficient UOR and energy-efficient hydrogen production. Our approach paves the way for scalable, cost-effective solutions that couple renewable energy generation with effective wastewater treatment.