This study evaluated the phytoremediation of mine tailing-contaminated soils in Quiulacocha, Peru, using the combined application of biochar and compost, with Zea mays L. (maize) serving as the phytoremediator due to its high biomass production and stress tolerance. A factorial experimental design was implemented, varying two main factors: the mining tailings dose (30% and 60% w/w) and the biochar pyrolysis temperature (300 °C and 500 °C). The mine tailings were characterized by high concentrations of heavy metals and unfavourable physico-chemical properties (pH, low organic matter), whereas the biochar, produced from pine forest residues, and the compost, derived from urban organic waste, exhibited attributes that enhance soil quality. During the pot experiment, response variables including the Bioconcentration Factor (BCF) and Translocation Factor (TF) for various metals were evaluated to assess the capacity for contaminant immobilization and their distribution between plant roots and aerial tissues. The results demonstrated that the incorporation of biochar and compost significantly improved soil quality by increasing pH, cation exchange capacity, and nutrient retention, while simultaneously reducing the bioavailability of heavy metals and limiting their translocation to the aerial parts of maize. Factorial analysis further indicated that both the tailings dose and biochar pyrolysis temperature significantly influenced the efficacy of the phytoremediation process. In conclusion, the combined application of biochar and compost presents an effective and sustainable strategy for rehabilitating mine tailing-contaminated soils by stabilizing heavy metals and promoting the safe growth of Zea mays L.

Acid-generating mining waste and polymer waste are two of the most persistent environmental problems facing the mining and manufacturing sectors, respectively. We have investigated the co-recovery of these disparate waste streams for the production of unfired cementitious paving blocks. We established a statistically optimized formulation using response surface methodology (RSM) and a central composite design (CCD). We systematically evaluated three process variables: air-curing time (4–37 days), dosage of the waste mixture (5–68% by weight of dry solids: acid-generating mining waste, hydrated lime, and recycled polymer in a waste-to-polymer mass ratio of 1:1), and type of polymeric aggregate (recycled PET flakes versus granulated rubber). Compressive strength ranged from 4.5 to 42.1 MPa across the 40 experimental conditions. The resulting quadratic model was clearly significant (F = 186.31, p < 0.0001) with solid predictive parameters (R² = 0.9796; R²pred = 0.9627; adequate precision = 42.47). Desirability-based optimization, which limited air curing to industrially feasible timeframes (7–28 days) and maximized waste utilization within a 10–50% by weight, identified PET with 12.4 days of curing and a 50% by weight waste mixture as the optimal configuration, predicting a compressive strength of 37.3 MPa. This value exceeds the 32 MPa threshold for Type I heavy-traffic paving blocks; however, confirmatory tests yielded 34.09 ± 1.08 MPa, indicating that production-scale use should include control of moisture content, compaction, and batch homogeneity. Scanning electron microscopy with energy-dispersive spectroscopy (SEM/EDS) and X-ray diffraction (XRD) demonstrated that PET inclusions promoted a denser and more continuous interfacial transition zone than shredded rubber, driven by physical entanglement and the pronounced microfilling effect of the fine waste particles.