Functionalized biochar from vegetable waste for phosphorus removal from aqueous solution and its potential use as a slow-release fertilizer

[Display omitted] •Non-edible vegetable waste was successfully converted into functional biochar via co-pyrolysis with metal chloride salts.•Zinc chloride-doped biochar (ZBC) showed the highest phosphorus adsorption capacity (47.83 mg/g) compared to pristine and magnesium-doped biochar.•ZBC released 42% of the adsorbed phosphorus over 336 h, demonstrating its potential as a slow-release fertilizer.•In a pot study with mung plants, ZBC-enriched soil enhanced plant growth and increased dry biomass, with a 17% higher mung bean yield compared TSP-mixed soil.•This approach highlights the potential of valorizing vegetable waste, contributing to nutrient recovery and supporting a circular economy. Agricultural runoff of phosphorus leads to the loss of this critical nutrient into the waterbodies and causes environmental problems like eutrophication. To tackle the growing concern, functionalized biochar as an adsorbent provides a sustainable method to capture the phosphorus from wastewater. Additionally, the P-laden biochar as a slow-release fertilizer improves plant nutrient uptake and crop yield. In this work, metal chloride-doped biochar derived from non-edible vegetable waste was prepared and applied as an adsorbent. Zinc chloride-doped biochar (ZBC) showed a better phosphorus adsorption capacity of 47.83 mg/g among the prepared biochar. The desorption study suggested that around 42 % of total adsorbed P was released within 336 h. The growth of mung plants over 70 days was monitored, along with mung bean yield, to assess the effectiveness of P-laden ZBC as a slow-release phosphorus fertilizer. The presented approach of non-edible waste valorization into slow-release fertilizer could contribute to tackling nutrient depletion and achieving a circular economy.